1. What are the different types of VSAM files available?
ESDS: Entry
Sequence Data Set
KSDS: Key Sequence Data Set
RRDS: Relative
Data Set
2. What is IDCAMS ?
IDCAMS is the Access Method
Services program. You run the IDCAMS program and supply AMS commands thru SYSIN.
(examples of AMS commands are DELETE, DEFINE, REPRO etc..).
3. Can AMS
commands be run from the TSO prompt ?
Yes
4. Syntax of AMS modal
commands ?
Note: these can be used only under IDCAMS and not from the
TSO prompt.
IF LASTCC(or MAXCC) >(or <,= etc..) value -
THEN -
DO -
command set (such as DELETE, DEFINE etc..)
ELSE -
DO -
command set
LASTCC - Condition code
from the last function(such as delete) executed
MAXCC - Max condition
code that was returned by any of the prev functions
SET is also a valid
AMS command. SET LASTCC (or MAXCC) = value
The maximum condition code is
16. A cond code of 4 indicates a warning. A cond code of 8 is usually
encountered on a DELETE of a dataset that is not present.
5. Under
IDCAMS , multiple functions can be executed, each of which returns a cond code.
What will be the condition code returned to the operating system ?
The
maximum condition code generated is returned as the condition code of the IDCAMS
step.
6. What is Control Interval, Control Area ?
Control
Interval is analogous to a physical block for QSAM files. It is the unit of i/o.
Must be between 512 bytes to 32 k. Usually either 2K or 4K. A larger control
interval increases performance for sequential processing while the reverse is
true for random access. Under CICS when a record is locked, the entire CI gets
locked.
Control area is a group of control intervals. CA is used during
allocation. CA size is calculated based on the allocation type (cyl, tracks or
records) and can be max of 1 cylinder
7. What is FREESPACE ?
Coded in the DEFINE as FREESPACE(ci ca) where ci is the percentage of
each control interval to be left free for insertions, ca is the percentage of
control intervals in each control area to be left empty.
8. How do you
decide on optimum values for CI, FREESPACE etc..?
CI size should be
based on record length, type of processing. Usually CI is 4K. If record length
is larger(>1K), chose 6K or 8K.
FREESPACE should be large if more
number of insertions are envisaged. Usual values are (20 20) when heavy updates
are expected. CI size can be calculated.
9. Would you specify FREESPACE
for an ESDS?
No. Because you cannot insert records in an ESDS, also when
you rewrite a record, it must be of the same length. Thus putting any value for
freespace does not make any sense.
10. What is SHAREOPTS ?
SHAREOPTS is a parameter in the DEFINE and specifies how an object can
be shared among users. It is coded as SHAREOPTS(a b), where a is the cross
region share option ie how two or more jobs on a single system can share the
file, while b is the cross system share option ie how two or more jobs on
different MVSes can share the file. Usual value is (2 3).
11. What is
the meaning of each of the values in SHAREOPTS(2 3)?
Value of 2 for
cross region means that the file can be processed simultaneously by multiple
users provided only one of them is an updater. Value of 3 for cross system means
that any number of jobs can process the file for input or output (VSAM does
nothing to ensure integrity).
12. How do you define a KSDS ?
DEFINE CLUSTER(cluster name) with the INDEXED parameter. Also specify
the ds name for the DATA component & the ds INDEX component. Other important
parms are RECORDSIZE, KEYS, SHAREOPTIONS.
13. How do you define an
ALTINDX ? How do you use ALTINDXs in batch, CICS pgms ?
DEFINE
ALTERNATEINDEX. Important paramters are RELATE where you specify the base
cluster name, KEYS, RECORDSIZE,SHAREOPTIONS,UNIQUEKEY(or NONUNIQUEKEY), DATA(ds
name for the data component), INDEX(ds name for the index component).
Then DEFINE PATH. Important paramters are NAME (ds name for the path),
PATHENTRY (ds name of the alternate index name), UPDATE(or NOUPDATE) which
specifies whether an alt index is updated when a update to the base cluster
takes place.
Then BLDINDEX. Parameters are INDATASET(ds name of base
cluster), OUTDATASET(ds name of AIX).
Using alternate indexes in batch
pgms:
In the JCL, you must have DD stmts for the cluster and for the
path(s). In the cobol pgm, SELECT .. ASSIGN TO ddname for base cluster RECORD
KEY IS... ALTERNATE RECORD KEY IS..
Using alternate indexes in CICS
pgms:
FCT entries must be created for both base cluster & the path.
To read using the alternate index, use the dd name of the path in CICS file
control commands.
14. What happens when you open an empty VSAM file in a
COBOL program for input?
A VSAM file that has never contained a record
is treated as unavailable. Attempting to open for input will fail. An empty file
can be opened for output only. When you open for output, COBOL will write a
dummy record to the file & then delete it out.
15. How do you
initialize a VSAM file before any operation? a VSAM with alternate index?
Can write a dummy program that just opens the file for output & then
closes it.
16. What does a file status of 02 on a VSAM indicate?
Duplicate alternate key . Happens on both input and output operation
17. How do you calculate record size of an alternate cluster? Give your
values for both unique and non-unique.
Unique Case: 5 + ( alt-key-length
+ primary-key )
Nonunique Case: 5 + ( alt-key-length + n * primary-key )
where n = # of duplicate records for the alternate key
????Any
one who knows - can you explain ?
18. What is the difference between
sequential files and ESDS files?
Sequential(QSAM) files can be created
on tape while ESDS files cannot.
Also, you can have ALTINDEX for an ESDS
while no such facility exists for QSAM files.
19. How do you load a VSAM
data set with records ?
Using the REPRO command.
20. How do you
define a GDG ?
Use the DEFINE GENERATIONDATAGROUP command. In the same
IDCAMS step, another dataset must be defined whose DCB parameters are used when
new generations of the GDG are created. This dataset is known as the model
dataset. The ds name of this model dataset must be the same as that of the GDG,
so use a disp of keep rather than catlg and also specify space=(trk,0)
21. Do all versions of the GDG have to be of the same record length ?
No, the DCB of the model dataset can be overridden when you allocate new
versions.
22. How are different versions of GDG named ?
base-file-name.GnnnnnV00 where nnnn= generation number (upto 255).
nnnn will be 0000 for the 1st generation.
23. Suppose 3
generations of a GDG exist. How would you reference the 1 st generation in the
JCL?
Use GDG name(-2).
24. Suppose a generation of GDG gets
created in a particular step of a proc. How would you refer the current
generation in a subsequent step? What would be the disposition of this
generation now?
Relative generation numbers are updated only at the end
of the job, not at the end of a step. To allocate a new generation, we would be
using (+1) with a DISP of (NEW,CATLG,DELETE). To refer to this in a subsequent
step in the same job, we would again use (+1) but with a DISP of SHR or OLD.
25. What more info you should give in the DD statement while defining
the next generation of a GDG?
Give (+1) as the generation number, give
(new,catlg) for disp, give space parameter, can give the dcb parameter if you
want to override the dcb of the model dataset.
26. Assuming that the
DEFINE jcl is not available, how do you get info about a VSAM file?s
organisation ?
Use the LISTCAT command.
27. During processing of
a VSAM file, some system error occurs and it is subsequently unusable . What do
you do ?
Run VERIFY.
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Showing posts with label IBM-MAINFRAME-VSAM. Show all posts
Showing posts with label IBM-MAINFRAME-VSAM. Show all posts
Virtual Storage Access Method (VSAM)
What are the different types of VSAM files available? Explain them
Virtual Storage Access Method(VSAM) is a disk storage system.It was implemented in OS/VS2 operating system.
Subsequently, it was used through out the MVS architecture.
VSAM comprises of the following access methods:
ESDS: Entry Sequence Data Set
KSDS: Key Sequence Data Set
RRDS: Relative Data Set
VSAM records can be of fixed or variable length.
These are organized in fixed size blocks, known as Control Intervals, and later into larger divisions known as Control Areas.
CI sizes are measured in terms of bytes, while CA sizes are measured in terms of disk tracks or cylinders.
ESDS : It contains the files which are interface specific and accessed through Relative Byte Address
KSDS : It contains the files which are interface specific and accessed through a secondary index
RRDS : It contains the files which are interface specific and accessed through Relative Record Number
Each file has two objects.
1. File object - represents the file itself. The methods of the file are used to perform DELETE,READ,REWRITE,UNLOCK,WRITE,STARTBR operations.
2. FileBrowse object - represents a browse operations on the file and the methods are used to perform ENDBR,READNEXT,READPREV,RESETBR
What is the syntax of AMS modal commands?
The following is the syntax of AMS modal commands:IF LASTCC(or MAXCC) >(or <,= etc..) value -
THEN -
DO -
command set (like DELETE, DEFINE etc..)
ELSE -
DO -
command set
where
LASTCC - Condition code from the last function(such as delete) executed
MAXCC - Max condition code that was returned by any of the prev functions
SET is also a valid AMS command. SET LASTCC (or MAXCC) = value
PS: These can be used only under IDCAMS and not from the TSO prompt.
b.) What is the maximum record length for the VSAM dataset?
The maximum size of a VSAM record is 1 Cylinder.
What is Control Interval, Control Area?
Control Interval:Control Interval is similar to the physical block for QSAM files. It is represented as the unit of I/). A control unit's range must be 512 bytes to 32 KB. It is preferable to use either 2KB or 4KB.
Control Interval with larger space will increase the performance for sequential processing. On contrary, the reverse is true for random access.
Control Area:
Control Area is a group of control intervals.
The way of filing the control area is similar to that of control interval
The number of control intervals for each control area depends on the reserved space at the time of dataset creation.
How do you define an ALTINDX ? How do you use ALTINDXs in batch, CICS programs?
a.) Issue the command DEFINE ALTERNATEINDEX. Important parameters are RELATE where the database cluster name is specified.KEYS, RECORDSIZE,SHAREOPTIONS,UNIQUEKEY(or NONUNIQUEKEY)
DATA(data source name for the data component), INDEX(data source name for the index component).
b.) Then issue the command DEFINE PATH.
Important parameters are NAME (data source name for the path),
PATHENTRY (data source name of the alternate index name),
UPDATE or NOUPDATE, that specifies the determination of alt index is updated when an update to the database cluster occurs
c.) Then issue the command BLDINDEX.
Important parameters are INDATASET (data source name of base cluster), OUTDATASET(data source name of AIX).
Using alternate indexes in batch programs:
JCL, has DD statements for cluster and for paths.
For the COBOL program :
The command SELECT ASIGN TO ddname For the base cluster RECORD KEY IS… ALTERNATE RECORD KEY IS… used
Using alternate indexes in CICS programs:
The creation of FCT entries are mandatory for both cluster and the path
Utilize the dd name of the path in CICS file control commands, by using the alternate index
We can define the KSDS cluster by two ways by using the file-aid or by using the IDCAMS Utility. Explain them.
KSDS cluster can be defined by-Using the file-aid
-or by using IDCAMS utility:
The record can be defined with average length of 100 and maximum length of 150, in IDCAMS, with key length 10 starting at 0.
The following example illustrates :
//step01 EXEC pgm=IDCAMS
//SYSIN DD *
DEFINE CLUSTER(NAME(userid.name.sample) -
VOLUMES(MVS801) -
RECORDSIZE(100 150) -
TRACKS(10 20)
KEYS(10 0) -
INDEXED ) -
DATA ( NAME(userid.name.sample.data)) -
INDEX( NAME(userid.name.sample.index)) -
/*
//
How do you convert flat files to VSAM files?
Flat files are converted into VSAM files by following process:- Identify the primary key, when the whole record can be primary key.
- Alternate key can also be used, if needed
- File is to be sorted by primary key or the whole record
- Utilize the SORT statement for dropping duplicates.
- A JCL command ( IDCAMS – Define Cluster) need to be submitted by using the result of sorting mechanism(mentioned above) as input
- Use the command IDCAMS REPRO for loading the flat file into the VSAM file.
What is the maximum record length for the VSAM dataset?
- The maximum record length for VSAM data set is 1 cylinder.- There can be SPANNED RECORDS that covers multiple CIs
- A Spanned Record can never cross a CA.
- The maximum value for a CA is 1 cylinder, so the VSAM record.
How do you define a GDG?
- The command DENFINE GENERATIONDATAGROUP is used for defining GDG- In IDCAMS, another dataset definition is mandatory, where DCB parameters are used when new GDG are created
- This data set is called as ‘Model dataset;
- The data set name must be the same that of the GDG
- Use a ‘disp’ instead of ‘catlg’ and specify the space=(trk,0)
What is a CI SPLIT ? What is a CA SPLIT ?
When the Control Interval does not have enough space, VSAM performs a split on CI by moving some of the records to the CIs that are free.In case of non-availability of free space, VSAM performs a control area split. This is done by new control area allocation and moving half of the CIs to it.
CI SPLIT :
- The movement of some records into another free CI in the same CA
- CI Split needs certain number of Input / Output operations. This leads to degradation of VSAM file
- The correct space is needed to allocate for CI
- The result is half-empty CIs on contrary to one full and one empty CI
CA SPLIT :
- CA Split is the process moving half of the records of one CA to a new CA
- The addition or deletion of records can not accommodate in the existing CA
- The result is two half-full CAs on contrary to one full and one empty CA
How did you refresh a VSAM file and how frequently you do it ?
- Refresh can be done on daily or weekly or monthly basis- Refreshing refers to DELETE / DEFINE the VSAM file
Step 1:
Deleting the existing VSAM file:
IF LASTCC =8 ; SET MAXCC=0
Step 2:
DEFINE VSAM-FILE(COND=(0,LT,STEP1)
Return-code = 8 when the file that is trying to delete does not exist.
Utilize the command VERIFY in TSO
Explain the information contained in CI
- Control information consists of Record Descriptor Field and Control Interval Descriptor Field.- Each CI contains one CIDF that consists of the last 4 bytes
- CIDF consists of information about the offset and length of free space in the CI
- In case of fixed size records, each CI contains 2 RDFs each RDF is of 3 bytes length
- In case of variable length size records, there will be a separate RDF for each record in the CI.
- The data portion of the CI should be in the multiples of 512 bytes / 2048 bytes.
- The maximum size of the CI is 32 KB.
- The size of index portion of CI could be any of these – 512, 1024,2048,4096
Explain the differences between VSAM and Non-VSAM files
1. - The AMS program is used for creation of VSAM files- ISPF panel or a standard JCL is used for creation of a NON-VSAM dataset.
2. - The VSAM information is stored in catalogs
- The NON-VSAM information is stored in VTOC as dataset labels
3. - The data set organization in VSAM files are Key sequenced, Entry sequenced and Relative record data sets
A data set is a physical records that are stored on a disk or tape , is a collection with a unique name
The data set is normally identified by the MVS with labels
The label information need to be supplied in JCL
- The data set organization in NON-VSAM files are sequenced, Indexed Sequential, Direct and partitioned
Difference between VSAM and Database Tables
1. -VSAM file can not run SQL queries. -VSAM lacks any kind of relation -VIEWS and SYNONYMS can not be defined on VSAM files -RDBMS concepts can not be applied in VSAM files.2. - SQL queries can be run in database table - Data fetching is more efficient than VSAM files - RDBMS concepts are applicable in DB2 database - ALIAS VIEWS can be defined on tables for sharing customized data.
What is meant by dirty read in VSAM?
- High degree of concurrent access to VSAM files is achieved by dirty read - It is done by avoiding the complications associated with CI and CA splits - The dirty read protocol is summarized as:- The VSAM file mandatorily be defined with cross-region SHARE POINTS 4. - The file allocation must be with DISP=SHR - ENQ must be followed for all operations of the files, for data set - Data set name is specified for ENQ name - Any string can be used for the ENQ gname - The user’s buffer must be refreshed with GET request, after obtaining a lock - No lock is held during a wait - DEQ function should be called at the end of all the file operations of enqueue.
What are the IDCAMS commands that can be used for VSAM and explain each of them.
- To modify the information for a catalog, alternate index, cluster or a path, ALTER command is used- DEFINE command is used for ALTERNATEINDEX, CLUSTER or PATH
- DELETE command is used for removing the catalog for a catalog, cluster, alternate index or path
- LISTCAT command lists the information about the dataset.
- PRINT command prints the contents of dataset
- REPRO command is used to copy the records from one file to another.
What is the purpose of the VERIFY function of IDCAMS?
- To re-sync the end of the file information with the catalog information, the VERIFY function is used.Virtual Storage Access Method (VSAM)
26) At OPEN, VSAM determines processing options in the following order
(d)
a) JCL, program, catalog
b) program, JCL, catalog
c) JCL, catalog, program
d) catalog, program, JCL
e) None
27) VSAM request macros (e.g., GET, PUT) point to which other macros? (c)
a) OPEN
b) ACB
c) RPL
d) CLOSE
e) b and c
f) None
28) If a program uses direct processing exclusively, DIR is specified in which macros? (c)
a) OPEN
b) ACB
c) RPL
d) CLOSE
e) b and c
f) None
29) VSAM processing options could be specified in (e)
a) Catalog
b) Program control blocks
c) JCL
d) None
e) All the above
30) Which of the following is not a COBOL verb? (d)
a) START
b) READ
c) DELETE
d) UPDATE
e) REWRITE
31) Which of the following is/are not supported by COBOL? (d)
a) Skip-sequential processing
b) RBA addressing
c) Replacing existing record
d) a and b
e) a, b and c
f) a and c
32) Which is a valid SHAREOPTIONS specification? (b)
a) SHR(2 2)
b) SHR(2 3)
c) SHR(4 1)
d) SHR(1 2)
e) None
33) For a data set defined with SPEED, which of the following is true? (a)
a) SPEED is effective for the initial load only.
b) SPEED is effective for all additions to the data set after initial load.
c) If the load program ABENDS, VERIFY can determine the HIGH-USED-RBA of the data set.
d) If the load program ABENDS, only those records remaining in buffers need to be added to the data set.
e) None
34) VERIFY cannot be used for (c)
a) Empty data set
b) LDS
c) a and b
d) None
35) For a data set defined with NOERASE, which of the following is not true? (a)
a) Desirable for sensitive data
b) Removes catalog entries
c) All the above
d) None
36) Buffer space cannot be specified in which of the following? (d)
a) DD statement
b) Assembler program
c) AMS DEFINE
d) COBOL program
37) How many data buffers are required for sequential processing to overlap I/O processing? (c)
a) 2
b) 3
c) 4
d) 5
38) When defining a KSDS, the best place to specify CISZ is generally (b)
a) At the cluster level
b) At the data level only
c) At the index level only
d) At both data and index levels
39) For direct processing the recommended number of data buffers is (b)
a) STRNO
b) STRNO+1
c) STRNO+2
d) STRNO+3
e) None
40) For 3380 DASD, TRK(50 5) results in which CA size for a KSDS defined with NOIMBED? (b)
a) 1 TRK
b) 5 TRKS
c) 15 TRKS
d) 50 TRKS
e) None
41) Suppose you are defining a multi-volume data set with VOL(A B) and five key ranges specified. Which of the following correctly indicates where each key range will be located? (c)
a) First key range on VOL A; second on B; third on A; etc.
b) First key range on VOL B; second on A; third on B; etc.
c) First key range on VOL A; remaining key ranges on B.
d) All key ranges on VOL A; B is used for overflow only.
e) All key ranges on VOL B; A is used for overflow only.
42) An alternate index can be defined for which cluster type? (b)
a) KSDS and RRDS
b) KSDS and ESDS
c) KSDS and LDS
d) KSDS only
e) KSDS, ESDS and RRDS
43) If an application program accesses a base cluster in alternate key sequence, then DD statements are needed for which data sets? (f)
a) Base cluster
b) Alternate index
c) Path
d) a and b
e) a and c
f) a, b and c
44) An alternate index itself is which cluster type? (d)
a) LDS
b) RRDS
c) ESDS
d) KSDS
e) None
45) Which of the following backs up data in CI mode? (b)
a) REPRO only
b) EXPORT only
c) Both REPRO and EXPORT
d) Neither REPRO nor EXPORT
46) Which of the following writes catalog information into the backup data set? (b)
a) REPRO only
b) EXPORT only
c) Both REPRO and EXPORT
d) Neither REPRO nor EXPORT
47) Which of the following requires a DELETE/DEFINE before the command can be used to restore an
existing data set? (a)
a) REPRO only
b) IMPORT only
c) Both REPRO and IMPORT
d) Neither REPRO nor IMPORT
48) With HBACKDS the use of apostrophes to enclose the dsname is (b)
a) Required
b) Used to exclude the TSO id as the high level qualifier
c) Required only if one or more segments are specified generically
d) Not allowed if the data set is password protected
a) JCL, program, catalog
b) program, JCL, catalog
c) JCL, catalog, program
d) catalog, program, JCL
e) None
27) VSAM request macros (e.g., GET, PUT) point to which other macros? (c)
a) OPEN
b) ACB
c) RPL
d) CLOSE
e) b and c
f) None
28) If a program uses direct processing exclusively, DIR is specified in which macros? (c)
a) OPEN
b) ACB
c) RPL
d) CLOSE
e) b and c
f) None
29) VSAM processing options could be specified in (e)
a) Catalog
b) Program control blocks
c) JCL
d) None
e) All the above
30) Which of the following is not a COBOL verb? (d)
a) START
b) READ
c) DELETE
d) UPDATE
e) REWRITE
31) Which of the following is/are not supported by COBOL? (d)
a) Skip-sequential processing
b) RBA addressing
c) Replacing existing record
d) a and b
e) a, b and c
f) a and c
32) Which is a valid SHAREOPTIONS specification? (b)
a) SHR(2 2)
b) SHR(2 3)
c) SHR(4 1)
d) SHR(1 2)
e) None
33) For a data set defined with SPEED, which of the following is true? (a)
a) SPEED is effective for the initial load only.
b) SPEED is effective for all additions to the data set after initial load.
c) If the load program ABENDS, VERIFY can determine the HIGH-USED-RBA of the data set.
d) If the load program ABENDS, only those records remaining in buffers need to be added to the data set.
e) None
34) VERIFY cannot be used for (c)
a) Empty data set
b) LDS
c) a and b
d) None
35) For a data set defined with NOERASE, which of the following is not true? (a)
a) Desirable for sensitive data
b) Removes catalog entries
c) All the above
d) None
36) Buffer space cannot be specified in which of the following? (d)
a) DD statement
b) Assembler program
c) AMS DEFINE
d) COBOL program
37) How many data buffers are required for sequential processing to overlap I/O processing? (c)
a) 2
b) 3
c) 4
d) 5
38) When defining a KSDS, the best place to specify CISZ is generally (b)
a) At the cluster level
b) At the data level only
c) At the index level only
d) At both data and index levels
39) For direct processing the recommended number of data buffers is (b)
a) STRNO
b) STRNO+1
c) STRNO+2
d) STRNO+3
e) None
40) For 3380 DASD, TRK(50 5) results in which CA size for a KSDS defined with NOIMBED? (b)
a) 1 TRK
b) 5 TRKS
c) 15 TRKS
d) 50 TRKS
e) None
41) Suppose you are defining a multi-volume data set with VOL(A B) and five key ranges specified. Which of the following correctly indicates where each key range will be located? (c)
a) First key range on VOL A; second on B; third on A; etc.
b) First key range on VOL B; second on A; third on B; etc.
c) First key range on VOL A; remaining key ranges on B.
d) All key ranges on VOL A; B is used for overflow only.
e) All key ranges on VOL B; A is used for overflow only.
42) An alternate index can be defined for which cluster type? (b)
a) KSDS and RRDS
b) KSDS and ESDS
c) KSDS and LDS
d) KSDS only
e) KSDS, ESDS and RRDS
43) If an application program accesses a base cluster in alternate key sequence, then DD statements are needed for which data sets? (f)
a) Base cluster
b) Alternate index
c) Path
d) a and b
e) a and c
f) a, b and c
44) An alternate index itself is which cluster type? (d)
a) LDS
b) RRDS
c) ESDS
d) KSDS
e) None
45) Which of the following backs up data in CI mode? (b)
a) REPRO only
b) EXPORT only
c) Both REPRO and EXPORT
d) Neither REPRO nor EXPORT
46) Which of the following writes catalog information into the backup data set? (b)
a) REPRO only
b) EXPORT only
c) Both REPRO and EXPORT
d) Neither REPRO nor EXPORT
47) Which of the following requires a DELETE/DEFINE before the command can be used to restore an
existing data set? (a)
a) REPRO only
b) IMPORT only
c) Both REPRO and IMPORT
d) Neither REPRO nor IMPORT
48) With HBACKDS the use of apostrophes to enclose the dsname is (b)
a) Required
b) Used to exclude the TSO id as the high level qualifier
c) Required only if one or more segments are specified generically
d) Not allowed if the data set is password protected
Virtual Storage Access Method (VSAM)
Choose the correct answer:
1) Which VSAM clusters support only fixed length records? (b)
a) LDS
b) RRDS
c) ESDS
d) KSDS
2) FREESPACE can be specified for which type of cluster? (d)
a) LDS
b) RRDS
c) ESDS
d) KSDS
3) In which cluster type are records added at the end of the data set? (c)
a) LDS
b) RRDS
c) ESDS
d) KSDS
4) The types of processing supported by RRDS are (e)
a) sequential
b) skip-sequential
c) direct
d) a and b
e) a, b and c
5) The types of processing supported by ESDS are (d)
a) sequential
b) skip-sequential
c) direct
d) a and b
e) a and c
6) Spanned records can be found in (d)
a) ESDS
b) KSDS
c) RRDS
d) a or b
e) a or c
7) Spanned records can be accessed in (a)
a) MOVE
b) LOCATE
c) a and b
d) None
8) Alternate Index is a special type of (a)
a) KSDS
b) ESDS
c) RRDS
d) None
9) Specifying CISZ(4096) at the cluster level for a KSDS results in (c)
a) VSAM ignoring the specification
b) Data and index CISZ 4k each
c) Data CISZ 4k; index CISZ selected by VSAM
d) Index CISZ 4K; data CISZ selected by VSAM
10) When defining a KSDS, which of the following parameters is not required? (b)
a) Space allocation (either CYL, REC or TRK)
b) VOLUMES
c) KEYS
d) NAME
11) Default RECORD SIZE for a NONSPANNED data set is (d)
a) (80 80)
b) (4086 32600)
c) (100 32600)
d) (4089 4089)
12) If the key of a KSDS record begins in the second field (first field is 25 bytes long), the offset in the
KEYS parameter is (a)
a) 24
b) 25
c) 26
d) None
13) Data organization in KSDS is (a)
a) INDEXED
b) NUMBERED
c) LINEAR
d) NONINDEXED
14) The default cluster type is (d)
a) ESDS
b) RRDS
c) LDS
d) KSDS
15) VOLUMES parameter can be specified at (c)
a) cluster level
b) data level and index level
c) All the above
d) None
16) The RECORDSIZE parameter cannot be coded for (c)
a) ESDS
b) RRDS
c) LDS
d) KSDS
17) The default PRINT format is (b)
a) Character
b) Dump
c) Hexadecimal
d) None
18) Which of the following REPRO selection parameters can be specified for an LDS? (e)
a) FROMKEY
b) FROMADDRESS
c) FROMNUMBER
d) SKIP
e) None
19) The REPLACE parameter causes (c)
a) KSDS records to be replaced by an input record with the same key
b) ESDS records to be replaced by an input record with the same RBA
c) RRDS records to be replaced by an input record with the same RRN
d) a and c
e) All the above
20) Which of the following is not a modal command? (e)
a) IF
b) THEN
c) ELSE
d) DO
e) GOTO
21) Using REPRO to reorganize a KSDS, which of the following is true? (e)
a) Input must be ascending key sequence.
b) No duplicate keys are allowed.
c) Non-unique keys are allowed.
d) a and c
e) a and b
22) Which of the following entry names are valid for ALTER FREESPACE? (b)
a) Cluster name
b) Data component name
c) Index component name
d) b and c
e) a, b and c
23) Which of the following is a correct generic name specification for TEST.USER.DATA.A? (a)
a) TEST.USER.*
b) TEST.*.*.A
c) *.USER.DATA.A
d) TEST.USER.*.A
24) To alter a cluster to an LDS, the cluster must (e)
a) be an ESDS
b) be NONSPANNED
c) have a CISZ of 4K
d) not have an alternate index associated with it
e) all the above
25) For which access mode below must the application program interpret RDFs? (b)
a) KEY
b) ADR
c) ADR(for a KSDS)
d) CNV
e) None
1) Which VSAM clusters support only fixed length records? (b)
a) LDS
b) RRDS
c) ESDS
d) KSDS
2) FREESPACE can be specified for which type of cluster? (d)
a) LDS
b) RRDS
c) ESDS
d) KSDS
3) In which cluster type are records added at the end of the data set? (c)
a) LDS
b) RRDS
c) ESDS
d) KSDS
4) The types of processing supported by RRDS are (e)
a) sequential
b) skip-sequential
c) direct
d) a and b
e) a, b and c
5) The types of processing supported by ESDS are (d)
a) sequential
b) skip-sequential
c) direct
d) a and b
e) a and c
6) Spanned records can be found in (d)
a) ESDS
b) KSDS
c) RRDS
d) a or b
e) a or c
7) Spanned records can be accessed in (a)
a) MOVE
b) LOCATE
c) a and b
d) None
8) Alternate Index is a special type of (a)
a) KSDS
b) ESDS
c) RRDS
d) None
9) Specifying CISZ(4096) at the cluster level for a KSDS results in (c)
a) VSAM ignoring the specification
b) Data and index CISZ 4k each
c) Data CISZ 4k; index CISZ selected by VSAM
d) Index CISZ 4K; data CISZ selected by VSAM
10) When defining a KSDS, which of the following parameters is not required? (b)
a) Space allocation (either CYL, REC or TRK)
b) VOLUMES
c) KEYS
d) NAME
11) Default RECORD SIZE for a NONSPANNED data set is (d)
a) (80 80)
b) (4086 32600)
c) (100 32600)
d) (4089 4089)
12) If the key of a KSDS record begins in the second field (first field is 25 bytes long), the offset in the
KEYS parameter is (a)
a) 24
b) 25
c) 26
d) None
13) Data organization in KSDS is (a)
a) INDEXED
b) NUMBERED
c) LINEAR
d) NONINDEXED
14) The default cluster type is (d)
a) ESDS
b) RRDS
c) LDS
d) KSDS
15) VOLUMES parameter can be specified at (c)
a) cluster level
b) data level and index level
c) All the above
d) None
16) The RECORDSIZE parameter cannot be coded for (c)
a) ESDS
b) RRDS
c) LDS
d) KSDS
17) The default PRINT format is (b)
a) Character
b) Dump
c) Hexadecimal
d) None
18) Which of the following REPRO selection parameters can be specified for an LDS? (e)
a) FROMKEY
b) FROMADDRESS
c) FROMNUMBER
d) SKIP
e) None
19) The REPLACE parameter causes (c)
a) KSDS records to be replaced by an input record with the same key
b) ESDS records to be replaced by an input record with the same RBA
c) RRDS records to be replaced by an input record with the same RRN
d) a and c
e) All the above
20) Which of the following is not a modal command? (e)
a) IF
b) THEN
c) ELSE
d) DO
e) GOTO
21) Using REPRO to reorganize a KSDS, which of the following is true? (e)
a) Input must be ascending key sequence.
b) No duplicate keys are allowed.
c) Non-unique keys are allowed.
d) a and c
e) a and b
22) Which of the following entry names are valid for ALTER FREESPACE? (b)
a) Cluster name
b) Data component name
c) Index component name
d) b and c
e) a, b and c
23) Which of the following is a correct generic name specification for TEST.USER.DATA.A? (a)
a) TEST.USER.*
b) TEST.*.*.A
c) *.USER.DATA.A
d) TEST.USER.*.A
24) To alter a cluster to an LDS, the cluster must (e)
a) be an ESDS
b) be NONSPANNED
c) have a CISZ of 4K
d) not have an alternate index associated with it
e) all the above
25) For which access mode below must the application program interpret RDFs? (b)
a) KEY
b) ADR
c) ADR(for a KSDS)
d) CNV
e) None
Virtual Storage Access Method (VSAM)
State whether True or False:
1. All VSAM data sets reside on DASD devices. (T)
2. Whenever a record is retrieved from DASD, the entire CA containing it is read into VSAM buffer. (F)
3. A LDS has no control information embedded in its CIs. (T)
4. In an RRDS, the position of a data record can be changed. (F)
5. Records from an ESDS can either be accessed sequentially or by RBA. (T)
6. Deletions and updating of records is possible in ESDS. (F)
7. Spanned records can only be used in ESDS or KSDS. (T)
8. Spanned records are records larger than CA size. (F)
9. A CI that contains the record segment of a spanned record contains no other data. (T)
10. Spanned records must be accessed in LOCATE mode. (F)
11. A KSDS has both data and index components. (T)
12. A newly inserted record is always added at the end of a KSDS. (F)
13. A new index entry is inserted in the sequence set record corresponding to a CI split. (T)
14. IMBED places the sequence set CI for a data control area within the control area. (T)
15. VSAM control intervals containing data records have at least one RDF and one CIDF.(T)
16. Control area sizes vary by device type. (F)
17. Control interval sizes vary by device type. (T)
18. For a KSDS, the larger the data CA size, the smaller the number of index CIs. (F)
19. We cannot access variable-length blocked records in VSAM. (F)
20. MCAT contains pointers to system data sets and user catalogs. (T)
21. While creating VSAM data sets, provision of component names is a must. (F)
22. JOBCAT identifies a default catalog for a single job step. (F)
23. There is a one-to-one correspondence between BCSs and VVDSs. (F)
24. The need for JOBCAT/STEPCAT statements has been replaced by the ALIAS. (T)
25. Aliases are limited to the first segment of the component name. (F)
26. The cluster name is required when defining VSAM cluster using DEFINE CLUSTER command. (T)
27. Any parameters in coded for the cluster in DEFINE CLUSTER will also apply to the data and index components. (T)
28. If the space allocation is coded at cluster level in DEFINE CLUSTER, the space is divided between data and index. (T)
29. If the specified CISZ is not valid in DEFINE CLUSTER, VSAM increases the number to the next valid CISZ. (T)
30. All the parameters for LISTCAT command are required. (F)
31. A data component name will be generated by AMS if it is not explicitly coded. (T)
32. DEFINE CLUSTER for a KSDS will generate cluster, data and index information even if only cluster information is specified. (T)
33. The candidate volume is not used when data set is initially loaded. (T)
34. Suppose TEST.DATASET is a KSDS. The following statement will print cluster information only:
35. LISTCAT ENTRIES (TEST.DATASET) ALL (F)
36. REPRO copies or merges an alternate index as an ESDS. (F)
37. A PRINT command prints only VSAM data sets. (F)
38. A KSDS can be printed only in key order. (F)
39. A RRDS is printed in relative record number sequence. (T)
40. The default print format is CHARACTER. (F)
41. Generic keys can be specified in PRINT FROMKEY and TOKEY. (T)
42. REPRO will stop processing records when a total of four physical I/O errors occur while writing to the
output data set. (F)
43. REPRO REUSE against a non-empty target data set defined with NOREUSE will reset the target data set. (F)
44. In altering a KSDS, BUFND and BUFNI can be specified instead of BUFFERSPACE.(F)
45. ALTER REMOVEVOLUMES will not remove the volume if the data set currently has data on the volume. (T)
46. ALTER can be used to change ESDS to LDS. (T)
47. ALTER NULLIFY can be used to nullify all passwords, except the master. (F)
48. ALTER modifies the cataloged attributes of a VSAM data set. (T)
49. Generic names can be used to rename a group of objects or to alter an attribute of a group of objects. (T)
50. Data Class specifications override the appropriate JCL parameters. (F)
51. Not all attributes can be specified through JCL. (T)
52. VSAM data can be read by logical record or by control interval access. (T)
53. OPEN causes VSAM to verify that the processing options match the cluster type. (T)
54. COBOL does not support skip-sequential processing. (T)
55. COBOL supports RBA addressing and backward processing. (F)
56. VS COBOL II supports skip-processing. (F)
57. Non-spanned records may be accessed in either MOVE or LOCATE mode. (T)
58. The ISAM interface program allows VSAM programs to access ISAM data sets. (F)
59. Cross system sharing is either between multiple systems or multiple virtual machines.(T)
60. Software end-of-file is a CI containing all zeroes excluding CIDF. (F)
61. VERIFY can be used for empty data sets. (F)
62. Catalog password protection is required for data set password checking. (T)
63. To ensure read integrity the application program must code ENQ/DEQ. (T)
64. For a data set with SHAREOPTIONS(4 3), CA splits are not allowed. (F)
65. The default for DELETE CLUSTER is NOERASE. (T)
66. If a cluster has VSAM password protection, the cluster MUST have a master password. (T)
67. The high-level index set record is maintained in the buffer if more than one index buffer (per string ) is provided. (T)
68. VSAM allocates index buffers for all cluster types, even if the buffers are never used.(T)
69. BUFND and BUFNI are preferable to BUFFERSPACE. (T)
70. STRNO is used for sharing data sets across regions. (T)
71. Data buffers and control blocks are allocated below 16M by default. (T)
72. Large control intervals decrease virtual storage requirement for buffers. (F)
73. Buffer space specified at ACB overrides the defined value, if the ACB value is more. (F)
74. The default for DEFINE CLUSTER is ERASE. (F)
75. A large percentage of unused CI free space causes additional I/Os when accessing the data set sequentially. (T) Sequential processing does not use CI free space beyond the free space threshold. (T)
76. The larger the free space, the more are the levels of index. (T)
77. Improved CI (ICI) access is available for logical record processing as well as CNV processing. (F)
78. Processing a large data set with multiple extents in DIR mode performs approximately as well as processing a large single extent data set in DIR mode. (F)
79. IMBED replicates the sequence set CI associated with a data CA on the first track of data CA.
80. REPLICATE imbeds the index set within the data component. (F)
81. In a multiple volume data set the first allocation of space on a volume is always a primary allocation. (T)
82. Index key compression can be suppressed with the NOCOMPRESS parameter. (F)
83. For sequential processing larger data CIs are desirable. (T)
84. Key compression applies to the keys of both index and data components. (F)
85. Multiple alternate indexes may be defined over a base cluster. (T)
86. Alternate indexes are spanned record data sets. (T)
87. The size of an alternate index is about the same size of its base cluster. (F)
88. AIX records may be longer than specified in the DEFINE AIX maximum record size.(T)
89. A path is required so that an application program can specify base cluster keys and retrieve alternate index records. (T)
90. Base cluster must be empty for BLDINDEX. (F)
91. Upgrade is done only for non-empty alternate indexes. (T)
92. After reorganizing a KSDS, the physical sequence of data is same as the logical sequence of data. (T)
93. Index component is however not reconstructed, after the reorganization of a KSDS. (F)
94. EXPORT extracts catalog information and creates a copy of the data records. (T)
95. Records larger than 32760 cause EXPORT in CIMODE to terminate with an error. (F)
96. CIMODE is the default for EXPORT of an LDS. (T)
97. The base cluster must be imported before the alternate indexes. (T)
98. The base cluster must be exported before the alternate indexes (F)
99. DFDSS can be used to reorganize a KSDS. (T)
100. If the HIGH-USED-RBA of the IMPORT OUTDATASET parameter is zero, then VSAM deletes and redefines the OUTDATASET before the IMPORT operation. (F)
101. ISMF can be used to create a DFHSM batch job stream. (T)
102. Data Set List line operator commands may effect more than one data set. (T)
1. All VSAM data sets reside on DASD devices. (T)
2. Whenever a record is retrieved from DASD, the entire CA containing it is read into VSAM buffer. (F)
3. A LDS has no control information embedded in its CIs. (T)
4. In an RRDS, the position of a data record can be changed. (F)
5. Records from an ESDS can either be accessed sequentially or by RBA. (T)
6. Deletions and updating of records is possible in ESDS. (F)
7. Spanned records can only be used in ESDS or KSDS. (T)
8. Spanned records are records larger than CA size. (F)
9. A CI that contains the record segment of a spanned record contains no other data. (T)
10. Spanned records must be accessed in LOCATE mode. (F)
11. A KSDS has both data and index components. (T)
12. A newly inserted record is always added at the end of a KSDS. (F)
13. A new index entry is inserted in the sequence set record corresponding to a CI split. (T)
14. IMBED places the sequence set CI for a data control area within the control area. (T)
15. VSAM control intervals containing data records have at least one RDF and one CIDF.(T)
16. Control area sizes vary by device type. (F)
17. Control interval sizes vary by device type. (T)
18. For a KSDS, the larger the data CA size, the smaller the number of index CIs. (F)
19. We cannot access variable-length blocked records in VSAM. (F)
20. MCAT contains pointers to system data sets and user catalogs. (T)
21. While creating VSAM data sets, provision of component names is a must. (F)
22. JOBCAT identifies a default catalog for a single job step. (F)
23. There is a one-to-one correspondence between BCSs and VVDSs. (F)
24. The need for JOBCAT/STEPCAT statements has been replaced by the ALIAS. (T)
25. Aliases are limited to the first segment of the component name. (F)
26. The cluster name is required when defining VSAM cluster using DEFINE CLUSTER command. (T)
27. Any parameters in coded for the cluster in DEFINE CLUSTER will also apply to the data and index components. (T)
28. If the space allocation is coded at cluster level in DEFINE CLUSTER, the space is divided between data and index. (T)
29. If the specified CISZ is not valid in DEFINE CLUSTER, VSAM increases the number to the next valid CISZ. (T)
30. All the parameters for LISTCAT command are required. (F)
31. A data component name will be generated by AMS if it is not explicitly coded. (T)
32. DEFINE CLUSTER for a KSDS will generate cluster, data and index information even if only cluster information is specified. (T)
33. The candidate volume is not used when data set is initially loaded. (T)
34. Suppose TEST.DATASET is a KSDS. The following statement will print cluster information only:
35. LISTCAT ENTRIES (TEST.DATASET) ALL (F)
36. REPRO copies or merges an alternate index as an ESDS. (F)
37. A PRINT command prints only VSAM data sets. (F)
38. A KSDS can be printed only in key order. (F)
39. A RRDS is printed in relative record number sequence. (T)
40. The default print format is CHARACTER. (F)
41. Generic keys can be specified in PRINT FROMKEY and TOKEY. (T)
42. REPRO will stop processing records when a total of four physical I/O errors occur while writing to the
output data set. (F)
43. REPRO REUSE against a non-empty target data set defined with NOREUSE will reset the target data set. (F)
44. In altering a KSDS, BUFND and BUFNI can be specified instead of BUFFERSPACE.(F)
45. ALTER REMOVEVOLUMES will not remove the volume if the data set currently has data on the volume. (T)
46. ALTER can be used to change ESDS to LDS. (T)
47. ALTER NULLIFY can be used to nullify all passwords, except the master. (F)
48. ALTER modifies the cataloged attributes of a VSAM data set. (T)
49. Generic names can be used to rename a group of objects or to alter an attribute of a group of objects. (T)
50. Data Class specifications override the appropriate JCL parameters. (F)
51. Not all attributes can be specified through JCL. (T)
52. VSAM data can be read by logical record or by control interval access. (T)
53. OPEN causes VSAM to verify that the processing options match the cluster type. (T)
54. COBOL does not support skip-sequential processing. (T)
55. COBOL supports RBA addressing and backward processing. (F)
56. VS COBOL II supports skip-processing. (F)
57. Non-spanned records may be accessed in either MOVE or LOCATE mode. (T)
58. The ISAM interface program allows VSAM programs to access ISAM data sets. (F)
59. Cross system sharing is either between multiple systems or multiple virtual machines.(T)
60. Software end-of-file is a CI containing all zeroes excluding CIDF. (F)
61. VERIFY can be used for empty data sets. (F)
62. Catalog password protection is required for data set password checking. (T)
63. To ensure read integrity the application program must code ENQ/DEQ. (T)
64. For a data set with SHAREOPTIONS(4 3), CA splits are not allowed. (F)
65. The default for DELETE CLUSTER is NOERASE. (T)
66. If a cluster has VSAM password protection, the cluster MUST have a master password. (T)
67. The high-level index set record is maintained in the buffer if more than one index buffer (per string ) is provided. (T)
68. VSAM allocates index buffers for all cluster types, even if the buffers are never used.(T)
69. BUFND and BUFNI are preferable to BUFFERSPACE. (T)
70. STRNO is used for sharing data sets across regions. (T)
71. Data buffers and control blocks are allocated below 16M by default. (T)
72. Large control intervals decrease virtual storage requirement for buffers. (F)
73. Buffer space specified at ACB overrides the defined value, if the ACB value is more. (F)
74. The default for DEFINE CLUSTER is ERASE. (F)
75. A large percentage of unused CI free space causes additional I/Os when accessing the data set sequentially. (T) Sequential processing does not use CI free space beyond the free space threshold. (T)
76. The larger the free space, the more are the levels of index. (T)
77. Improved CI (ICI) access is available for logical record processing as well as CNV processing. (F)
78. Processing a large data set with multiple extents in DIR mode performs approximately as well as processing a large single extent data set in DIR mode. (F)
79. IMBED replicates the sequence set CI associated with a data CA on the first track of data CA.
80. REPLICATE imbeds the index set within the data component. (F)
81. In a multiple volume data set the first allocation of space on a volume is always a primary allocation. (T)
82. Index key compression can be suppressed with the NOCOMPRESS parameter. (F)
83. For sequential processing larger data CIs are desirable. (T)
84. Key compression applies to the keys of both index and data components. (F)
85. Multiple alternate indexes may be defined over a base cluster. (T)
86. Alternate indexes are spanned record data sets. (T)
87. The size of an alternate index is about the same size of its base cluster. (F)
88. AIX records may be longer than specified in the DEFINE AIX maximum record size.(T)
89. A path is required so that an application program can specify base cluster keys and retrieve alternate index records. (T)
90. Base cluster must be empty for BLDINDEX. (F)
91. Upgrade is done only for non-empty alternate indexes. (T)
92. After reorganizing a KSDS, the physical sequence of data is same as the logical sequence of data. (T)
93. Index component is however not reconstructed, after the reorganization of a KSDS. (F)
94. EXPORT extracts catalog information and creates a copy of the data records. (T)
95. Records larger than 32760 cause EXPORT in CIMODE to terminate with an error. (F)
96. CIMODE is the default for EXPORT of an LDS. (T)
97. The base cluster must be imported before the alternate indexes. (T)
98. The base cluster must be exported before the alternate indexes (F)
99. DFDSS can be used to reorganize a KSDS. (T)
100. If the HIGH-USED-RBA of the IMPORT OUTDATASET parameter is zero, then VSAM deletes and redefines the OUTDATASET before the IMPORT operation. (F)
101. ISMF can be used to create a DFHSM batch job stream. (T)
102. Data Set List line operator commands may effect more than one data set. (T)
Virtual Storage Access Method (VSAM)
Q76) How many buffers are allotted to VSAM KSDS and ESDS?A76) 2 data
buffers by default for ESDS. For KSDS it allots 2 data buffers and 1 index
buffers. each buffer is about 4k.
Q77) what's the biggest disadvantage of using a VSAM dataset?A77) FREE SPACE(FPSC)
Q78) what's the device independent method to indicate where a Record is Stored?A78) By USING RBA(Relative Byte Address).
Q79) How many times secondary space allocated?A79) 122 TIMES
Q80) what is the RRN for the first record in RRDS?A80) The answer is : 1
Q81) what is a Base Cluster?A81) The Index and data components of a KSDS
Q82) If FSPC(100 100) is specified does it mean that both the control interval and control area will be left empty because 100 % of both CI and ca are specified to be empty?82) No, they would not be left empty. one record will be written in each CI and 1 CI will be written for each ca.
Q77) what's the biggest disadvantage of using a VSAM dataset?A77) FREE SPACE(FPSC)
Q78) what's the device independent method to indicate where a Record is Stored?A78) By USING RBA(Relative Byte Address).
Q79) How many times secondary space allocated?A79) 122 TIMES
Q80) what is the RRN for the first record in RRDS?A80) The answer is : 1
Q81) what is a Base Cluster?A81) The Index and data components of a KSDS
Q82) If FSPC(100 100) is specified does it mean that both the control interval and control area will be left empty because 100 % of both CI and ca are specified to be empty?82) No, they would not be left empty. one record will be written in each CI and 1 CI will be written for each ca.
Virtual Storage Access Method (VSAM)
Q51) How do you calculate record size of an alternate cluster? Give your values
for both unique and nonunique.Q51) Unique Case: 5 + ( alt-key-length +
primary-key )
Non unique Case: 5 + ( alt-key-length + n * primary-key ) where n = number of duplicate records for the alternate key
Q52) What is the difference between sequential files and ESDS files?Q52) Sequential (QSAM) files can be created on tape while ESDS files cannot. Also, you can have ALTINDEX for an ESDS while no such facility exists for QSAM files.
Q53) How do you load a VSAM data set with records ?Q53) Using the REPRO command.
Q54) How do you define a GDG ?Q54) Use the DEFINE GENERATIONDATAGROUP command. In the same IDCAMS step, another dataset must be defined whose DCB parameters are used when new generations of the GDG are created. This dataset is known as the model dataset. The ds name of this model dataset must be the same as that of the GDG, so use a disp of keep rather than catlg and also specify space=(trk,0)
Q55) Do all versions of the GDG have to be of the same record length ?Q55) No, the DCB of the model dataset can be overridden when you allocate new versions.
Q56) How are different versions of GDG named ?Q56) base-file-name.GnnnnnV00 where nnnn= generation number (upto 255). nnnn will be 0000 for the 1st generation.
Q57) Suppose 3 generations of a GDG exist. How would you reference the 1st generation in the JCL? - GSQ57) Use GDG name(-2).
Q58) Suppose a generation of GDG gets created in a particular step of a proc. How would you refer the current generation in a subsequent step? What would be the disposition of this generation now? - GSQ58) Relative generation numbers are updated only at the end of the job, not at the end of a step. To allocate a new generation, we would be using (+1) with a DISP of (NEW,CATLG,DELETE). To refer to this in a subsequent step in the same job, we would again use (+1) but with a DISP of SHR or OLD.
Q59) What more info you should give in the DD statement while defining the next generation of a GDG? - GSQ59) Give (+1) as the generation number, give (new,catlg) for disp, give space parameter, can give the DCB parameter if you want to override the dcb of the model dataset.
Q60) Assuming that the DEFINE JCL is not available, how do you get info about a VSAM file's organisation?Q60) Use the LISTCAT command.
Q61) During processing of a VSAM file, some system error occurs and it is subsequently unusable . What do you do ?Q61) Run VERIFY.
Q62) How do you fix the problem associated with VSAM out of space condition?Q62) Define new VSAM dataset allocated with more space.
Use IDCAMS to REPRO the old VSAM file to new VSAM dataset.
Use IDCAMS to ALTER / rename the old VSAM dataset or se IDCAMS to DELETE the old VSAM dataset.
Use IDCAMS to ALTER / rename the new VSAM dataset to the name of the original VSAM dataset.
Q63) What is the meaning of VSAM RETURN-CODE 28?Q63) Out of space condition is raised.
Q64) On which datasets You can have ALT INDEX?.Q64) only on KSDS and ESDS - not RRDS
Q65) How many Alternate Indexes you can have on a dataset?Q65) 255 - but you must be a nut to have so many ALT Indexes on a dataset!
Q66) Is it slower if you access a record through ALT INDEX as compared to Primary INDEX?Q66) Yes. Why? Because the alternate key would first locate the primary key, which in turn locates the actual record. Needs twice the number of I/Os.
Q67) What is RECOVERY and SPEED parameters in DEFINE CLUSTER command?Q67) RECOVERY (default) and SPEED are mutually exclusive. Recovery preformats the control areas during the initial dataset load, if the job fails, you can restart but you must have a recovery routine already written to restart the job. SPEED does not preformat the CAs. It is recommended that you specify SPEED to speed up your initial data load.
Q68) Describe SHAREOPTIONS parameter (SHR) in Define Cluster command.Q68) It defines the cross-region and cross-system sharing capabilities of the dataset. Syntax is SHR(Crvalue, CSvalue) value 1 means multiple read OR single write (read integrity) 2 means multiple read AND single write (Write integrity) 3 means Multiple read AND multiple write 4 is same as 3, which refreshes the buffer with every random access. default is SHR(1 3).
Q69) What does the KEYRANGES parameter in Define Cluster commend do?A69) It divides a large dataset into several volumes according to the Key ranges specified. e.g., KEYRANGES ((0000001 2999999) (3000000 5999999)). if the activity on the key ranges are evenly distributed, concurrent access is possible, which is a performance improvement.
Q70) What are the optional parameters to the input dataset While loading the empty cluster with the data records?70) 1)FROMADDRESS(address) 2)TOADDRESS(address) where 'address' specifies the RBA value of the key of the input record. 3)FROMNUMBER(rrn) 4)TONUMBER(rrn) where 'rrn' specifies the relative record number of the RRDS record 5)FROMKEY(key) 6)TOKEY(key) where 'key' specifies the key of the input record 7)SKIP(number) 8)COUNT(number) where 'number' specifies the number of records to skip or copy Ex: REPRO INFILE(DD1) OUTFILE(DD2) SKIP(9000) COUNT(700) - Skips the first 9000 records and begins copying at 9001 and copies 700 records from DD1 to DD2.
Q71) What is IDCAMS? and what is the purpose of it?.A71) IDCAMS is an access method services utility used for creating, deleting, altering VSAM files and copying sequential file to a VSAM file, etc.
Q72) How to delete a member using JCL.A72) Using IDCAMS a member can be deleted. DELETE 'XXX.YYY(member)
Q73) What is the Difference between LDS & ESDS ?A73) These two datasets are VSAM datasets. ESDS maintains control information. But LDS does not maintains the control information.
Q74) Is a delete operation possible in an ESDS?B. Is rewrite operation possible in ESDS ?A74) No delete operation is not possible in VSAM ESDS.B. Yes rewrite operation is possible in an ESDS.
Q75) What is an alternate index and path ?A75) An alternate index is an another way of accessing key sequenced data record stored in a base cluster and path is the linkage which connect alternate index to its base cluster.
Non unique Case: 5 + ( alt-key-length + n * primary-key ) where n = number of duplicate records for the alternate key
Q52) What is the difference between sequential files and ESDS files?Q52) Sequential (QSAM) files can be created on tape while ESDS files cannot. Also, you can have ALTINDEX for an ESDS while no such facility exists for QSAM files.
Q53) How do you load a VSAM data set with records ?Q53) Using the REPRO command.
Q54) How do you define a GDG ?Q54) Use the DEFINE GENERATIONDATAGROUP command. In the same IDCAMS step, another dataset must be defined whose DCB parameters are used when new generations of the GDG are created. This dataset is known as the model dataset. The ds name of this model dataset must be the same as that of the GDG, so use a disp of keep rather than catlg and also specify space=(trk,0)
Q55) Do all versions of the GDG have to be of the same record length ?Q55) No, the DCB of the model dataset can be overridden when you allocate new versions.
Q56) How are different versions of GDG named ?Q56) base-file-name.GnnnnnV00 where nnnn= generation number (upto 255). nnnn will be 0000 for the 1st generation.
Q57) Suppose 3 generations of a GDG exist. How would you reference the 1st generation in the JCL? - GSQ57) Use GDG name(-2).
Q58) Suppose a generation of GDG gets created in a particular step of a proc. How would you refer the current generation in a subsequent step? What would be the disposition of this generation now? - GSQ58) Relative generation numbers are updated only at the end of the job, not at the end of a step. To allocate a new generation, we would be using (+1) with a DISP of (NEW,CATLG,DELETE). To refer to this in a subsequent step in the same job, we would again use (+1) but with a DISP of SHR or OLD.
Q59) What more info you should give in the DD statement while defining the next generation of a GDG? - GSQ59) Give (+1) as the generation number, give (new,catlg) for disp, give space parameter, can give the DCB parameter if you want to override the dcb of the model dataset.
Q60) Assuming that the DEFINE JCL is not available, how do you get info about a VSAM file's organisation?Q60) Use the LISTCAT command.
Q61) During processing of a VSAM file, some system error occurs and it is subsequently unusable . What do you do ?Q61) Run VERIFY.
Q62) How do you fix the problem associated with VSAM out of space condition?Q62) Define new VSAM dataset allocated with more space.
Use IDCAMS to REPRO the old VSAM file to new VSAM dataset.
Use IDCAMS to ALTER / rename the old VSAM dataset or se IDCAMS to DELETE the old VSAM dataset.
Use IDCAMS to ALTER / rename the new VSAM dataset to the name of the original VSAM dataset.
Q63) What is the meaning of VSAM RETURN-CODE 28?Q63) Out of space condition is raised.
Q64) On which datasets You can have ALT INDEX?.Q64) only on KSDS and ESDS - not RRDS
Q65) How many Alternate Indexes you can have on a dataset?Q65) 255 - but you must be a nut to have so many ALT Indexes on a dataset!
Q66) Is it slower if you access a record through ALT INDEX as compared to Primary INDEX?Q66) Yes. Why? Because the alternate key would first locate the primary key, which in turn locates the actual record. Needs twice the number of I/Os.
Q67) What is RECOVERY and SPEED parameters in DEFINE CLUSTER command?Q67) RECOVERY (default) and SPEED are mutually exclusive. Recovery preformats the control areas during the initial dataset load, if the job fails, you can restart but you must have a recovery routine already written to restart the job. SPEED does not preformat the CAs. It is recommended that you specify SPEED to speed up your initial data load.
Q68) Describe SHAREOPTIONS parameter (SHR) in Define Cluster command.Q68) It defines the cross-region and cross-system sharing capabilities of the dataset. Syntax is SHR(Crvalue, CSvalue) value 1 means multiple read OR single write (read integrity) 2 means multiple read AND single write (Write integrity) 3 means Multiple read AND multiple write 4 is same as 3, which refreshes the buffer with every random access. default is SHR(1 3).
Q69) What does the KEYRANGES parameter in Define Cluster commend do?A69) It divides a large dataset into several volumes according to the Key ranges specified. e.g., KEYRANGES ((0000001 2999999) (3000000 5999999)). if the activity on the key ranges are evenly distributed, concurrent access is possible, which is a performance improvement.
Q70) What are the optional parameters to the input dataset While loading the empty cluster with the data records?70) 1)FROMADDRESS(address) 2)TOADDRESS(address) where 'address' specifies the RBA value of the key of the input record. 3)FROMNUMBER(rrn) 4)TONUMBER(rrn) where 'rrn' specifies the relative record number of the RRDS record 5)FROMKEY(key) 6)TOKEY(key) where 'key' specifies the key of the input record 7)SKIP(number) 8)COUNT(number) where 'number' specifies the number of records to skip or copy Ex: REPRO INFILE(DD1) OUTFILE(DD2) SKIP(9000) COUNT(700) - Skips the first 9000 records and begins copying at 9001 and copies 700 records from DD1 to DD2.
Q71) What is IDCAMS? and what is the purpose of it?.A71) IDCAMS is an access method services utility used for creating, deleting, altering VSAM files and copying sequential file to a VSAM file, etc.
Q72) How to delete a member using JCL.A72) Using IDCAMS a member can be deleted. DELETE 'XXX.YYY(member)
Q73) What is the Difference between LDS & ESDS ?A73) These two datasets are VSAM datasets. ESDS maintains control information. But LDS does not maintains the control information.
Q74) Is a delete operation possible in an ESDS?B. Is rewrite operation possible in ESDS ?A74) No delete operation is not possible in VSAM ESDS.B. Yes rewrite operation is possible in an ESDS.
Q75) What is an alternate index and path ?A75) An alternate index is an another way of accessing key sequenced data record stored in a base cluster and path is the linkage which connect alternate index to its base cluster.
Virtual Storage Access Method (VSAM)
Q26) What is a VSAM slot?Q26) A relative record dataset (RRDS) consists
of a specified number of areas called slots. Each slot is identified by a
relative record number (RRN) which indicates its relative position in the
file.
Q27) What is the utility program closely associated with VSAM?Q27) IDCAMS, the access method services utility.
Q28) There are at least seven IDCAMS commands; name and explain each of them ?.Q28) ALTER modifies information for a catalog, alternate index, cluster or path. BLDINDEX builds the alternate index, of course. DEFINE is used for ALTERNATEINDEX, CLUSTER or PATH. DELETE removes the catalog entry for a catalog, cluster, alternate index or path. LISTCAT lists information about the dataset. PRINT prints the dataset contents. REPRO copies records from one file to another.
Q29) What are the three levels of definition for the VSAM DEFINE?Q29) They are DEFINE CLUSTER, DATA and INDEX.
Q30) What is the significance of the SHAREOPTIONS parameter?Q30) It specifies how the file may be shared between jobs and between batch and CICS environments.
Q31) What is the meaning of the DEFINE MODEL parameter?Q31) It specifies whether Daniela Pestova or Yamila - oops! Wrong models! The MODEL parameter allows you to model your cluster by modeling it after an existing cluster.
Q32) What is File Status in VSAM?Q32) The FILE STATUS clause of the FILE-CONTROL paragraph allows for each file to be associated with a file status key (i.e., the 2-character data item specified in the FILE STATUS clause). If the FILE STATUS clause is specified for a given file, a value indicating the status of each I/O operation against that file is placed in the associated file status key. This value is stored in the file status key as soon as the I/O operation is completed (and before execution of any EXCEPTION/ERROR declarative or INVALIDKEY/AT END phrase associated with the I/O request).
Note: This element may behave differently when the CMPR2 compiler option is used. The file status key is divided
into two status keys: the first character is known as file status key 1; the second character is file status key 2.
Q33) What's a LDS (Linear Data Set) and what's it used for?Q33) LDS is a VSAM dataset in name only. It has unstructured 4k (4096 bytes) fixed size CI’s which do not contain control fields and therefore from VSAM's standpoint they do not contain any logical records. There is no free space, and no access from Cobol. Can be accessed by DB2 and IMS fast path datasets. LDS is essentially a table of data maintained on disk. The 'table entries' must be created via a user program and can only be logically accessed via a user program. When passed, the entire LDS must be mapped into storage, and then data is accessed via base and displacement type processing.
Q34) What is IDCAMS ?Q34) IDCAMS is the Access Method Services program. You run the IDCAMS program and supply AMS commands thru SYSIN. (examples of AMS commands are DELETE, DEFINE, REPRO etc..).
Q35) Can AMS commands be run from the TSO prompt ?Q35) Yes
Q36) Syntax of AMS modal commands ?Q36) Note: these can be used only under IDCAMS and not from the TSO prompt.
IF LASTCC(or MAXCC) >(or <,= etc..) value -
THEN -
DO -
command set (such as DELETE, DEFINE etc..)
ELSE -
DO -
command set
LASTCC - Condition code from the last function (such as delete) executed
MAXCC - Max condition code that was returned by any of the prev functions
SET is also a valid AMS command. SET LASTCC (or MAXCC) = value
The maximum condition code is 16. A cond code of 4 indicates a warning. A cond code of 8 is usually encountered on a DELETE of a dataset that is not present.
Q37) Under IDCAMS , multiple functions can be executed, each of which returns a cond code. What will be the condition code returned to the operating system ?Q37) The maximum condition code generated is returned as the condition code of the IDCAMS step.
38) What is Control Interval, Control Area?Q38) Control Interval is analogous to a physical block for QSAM files. It is the unit of I/O. Must be between 512 bytes to 32 k. Usually either 2K or 4K. A larger control interval increases performance for sequential processing while the reverse is true for random access. Under CICS when a record is locked, the entire CI gets locked.
Control Area is a group of control intervals. CA is used during allocation. CA size is calculated based on the
allocation type (cyl, tracks or records) and can be max of 1 cylinder
Q39) What is FREESPACE ?Q39) Coded in the DEFINE as FREESPACE(ci ca) where ci is the percentage of each control interval to be left free for insertions, ca is the percentage of control intervals in each control area to be left empty.
Q40) How do you decide on optimum values for CI, FREESPACE etc...?Q40) CI size should be based on record length, type of processing. Usually CI is 4K. If record length is larger(>1K), chose 6K or 8K. FREESPACE should be large if more number of insertions are envisaged. Usual values are (20 20) when heavy updates are expected. CI size can be calculated.
Q41) Would you specify FREESPACE for an ESDS?Q41) No. Because you cannot insert records in an ESDS, also when you rewrite a record, it must be of the same length. Thus putting any value for freespace does not make any sense.
Q42) What is SHAREOPTS ?Q42) SHAREOPTS is a parameter in the DEFINE and specifies how an object can be shared among users. It is coded as SHAREOPTS(a b), where a is the cross region share option ie how two or more jobs on a single system can share the file, while b is the cross system share option ie how two or more jobs on different MVS’s can share the file. Usual value is (2 3).
Q43) What is the meaning of each of the values in SHAREOPTS(2 3)?Q43) Value of 2 for cross region means that the file can be processed simultaneously by multiple users provided only one of them is an updater. Value of 3 for cross system means that any number of jobs can process the file for input or output (VSAM does nothing to ensure integrity).
Q44) How do you define a KSDS ?Q44) DEFINE CLUSTER(cluster name) with the INDEXED parameter. Also specify the ds name for the DATA component & the ds INDEX component. Other important parms are RECORDSIZE, KEYS, SHAREOPTIONS.
Q45) How do you define an ALTINDX ? How do you use ALTINDXs in batch, CICS pgm’s ?Q45) DEFINE ALTERNATEINDEX. Important paramters are RELATE where you specify the base cluster name, KEYS, RECORDSIZE,SHAREOPTIONS,UNIQUEKEY(or NONUNIQUEKEY), DATA(ds name for the data component), INDEX(ds name for the index component). Then DEFINE PATH. Important paramters are NAME (ds name for the path), PATHENTRY (ds name of the alternate index name), UPDATE(or NOUPDATE) which specifies whether an alt index is updated when a update to the base cluster takes place. Then BLDINDEX. Parameters are INDATASET(ds name of base cluster), OUTDATASET(ds name of AIX).
Q46) Using Alternate Indexes in Batch pgms:Q46) In the JCL, you must have DD stmts for the cluster and for the path(s). In the COBOL Program, SELECT .. ASSIGN TO ddname for base cluster RECORD KEY IS... ALTERNATE RECORD KEY IS..
Q47) Using Alternate Indexes in CICS pgms:Q47) FCT entries must be created for both base cluster & the path. To read using the alternate index, use the dd name of the path in CICS file control commands.
Q48) What happens when you open an empty VSAM file in a COBOL program for input?Q48) A VSAM file that has never contained a record is treated as unavailable. Attempting to open for input will fail. An empty file can be opened for output only. When you open for output, COBOL will write a dummy record to the file & then delete it out.
Q49) How do you initialize a VSAM file before any operation? a VSAM with alternate index?Q49) Can write a dummy program that just opens the file for output and then closes it.
Q50) What does a file status of 02 on a VSAM indicate?Q50) Duplicate alternate key . Happens on both input and output operation
Q27) What is the utility program closely associated with VSAM?Q27) IDCAMS, the access method services utility.
Q28) There are at least seven IDCAMS commands; name and explain each of them ?.Q28) ALTER modifies information for a catalog, alternate index, cluster or path. BLDINDEX builds the alternate index, of course. DEFINE is used for ALTERNATEINDEX, CLUSTER or PATH. DELETE removes the catalog entry for a catalog, cluster, alternate index or path. LISTCAT lists information about the dataset. PRINT prints the dataset contents. REPRO copies records from one file to another.
Q29) What are the three levels of definition for the VSAM DEFINE?Q29) They are DEFINE CLUSTER, DATA and INDEX.
Q30) What is the significance of the SHAREOPTIONS parameter?Q30) It specifies how the file may be shared between jobs and between batch and CICS environments.
Q31) What is the meaning of the DEFINE MODEL parameter?Q31) It specifies whether Daniela Pestova or Yamila - oops! Wrong models! The MODEL parameter allows you to model your cluster by modeling it after an existing cluster.
Q32) What is File Status in VSAM?Q32) The FILE STATUS clause of the FILE-CONTROL paragraph allows for each file to be associated with a file status key (i.e., the 2-character data item specified in the FILE STATUS clause). If the FILE STATUS clause is specified for a given file, a value indicating the status of each I/O operation against that file is placed in the associated file status key. This value is stored in the file status key as soon as the I/O operation is completed (and before execution of any EXCEPTION/ERROR declarative or INVALIDKEY/AT END phrase associated with the I/O request).
Note: This element may behave differently when the CMPR2 compiler option is used. The file status key is divided
into two status keys: the first character is known as file status key 1; the second character is file status key 2.
Q33) What's a LDS (Linear Data Set) and what's it used for?Q33) LDS is a VSAM dataset in name only. It has unstructured 4k (4096 bytes) fixed size CI’s which do not contain control fields and therefore from VSAM's standpoint they do not contain any logical records. There is no free space, and no access from Cobol. Can be accessed by DB2 and IMS fast path datasets. LDS is essentially a table of data maintained on disk. The 'table entries' must be created via a user program and can only be logically accessed via a user program. When passed, the entire LDS must be mapped into storage, and then data is accessed via base and displacement type processing.
Q34) What is IDCAMS ?Q34) IDCAMS is the Access Method Services program. You run the IDCAMS program and supply AMS commands thru SYSIN. (examples of AMS commands are DELETE, DEFINE, REPRO etc..).
Q35) Can AMS commands be run from the TSO prompt ?Q35) Yes
Q36) Syntax of AMS modal commands ?Q36) Note: these can be used only under IDCAMS and not from the TSO prompt.
IF LASTCC(or MAXCC) >(or <,= etc..) value -
THEN -
DO -
command set (such as DELETE, DEFINE etc..)
ELSE -
DO -
command set
LASTCC - Condition code from the last function (such as delete) executed
MAXCC - Max condition code that was returned by any of the prev functions
SET is also a valid AMS command. SET LASTCC (or MAXCC) = value
The maximum condition code is 16. A cond code of 4 indicates a warning. A cond code of 8 is usually encountered on a DELETE of a dataset that is not present.
Q37) Under IDCAMS , multiple functions can be executed, each of which returns a cond code. What will be the condition code returned to the operating system ?Q37) The maximum condition code generated is returned as the condition code of the IDCAMS step.
38) What is Control Interval, Control Area?Q38) Control Interval is analogous to a physical block for QSAM files. It is the unit of I/O. Must be between 512 bytes to 32 k. Usually either 2K or 4K. A larger control interval increases performance for sequential processing while the reverse is true for random access. Under CICS when a record is locked, the entire CI gets locked.
Control Area is a group of control intervals. CA is used during allocation. CA size is calculated based on the
allocation type (cyl, tracks or records) and can be max of 1 cylinder
Q39) What is FREESPACE ?Q39) Coded in the DEFINE as FREESPACE(ci ca) where ci is the percentage of each control interval to be left free for insertions, ca is the percentage of control intervals in each control area to be left empty.
Q40) How do you decide on optimum values for CI, FREESPACE etc...?Q40) CI size should be based on record length, type of processing. Usually CI is 4K. If record length is larger(>1K), chose 6K or 8K. FREESPACE should be large if more number of insertions are envisaged. Usual values are (20 20) when heavy updates are expected. CI size can be calculated.
Q41) Would you specify FREESPACE for an ESDS?Q41) No. Because you cannot insert records in an ESDS, also when you rewrite a record, it must be of the same length. Thus putting any value for freespace does not make any sense.
Q42) What is SHAREOPTS ?Q42) SHAREOPTS is a parameter in the DEFINE and specifies how an object can be shared among users. It is coded as SHAREOPTS(a b), where a is the cross region share option ie how two or more jobs on a single system can share the file, while b is the cross system share option ie how two or more jobs on different MVS’s can share the file. Usual value is (2 3).
Q43) What is the meaning of each of the values in SHAREOPTS(2 3)?Q43) Value of 2 for cross region means that the file can be processed simultaneously by multiple users provided only one of them is an updater. Value of 3 for cross system means that any number of jobs can process the file for input or output (VSAM does nothing to ensure integrity).
Q44) How do you define a KSDS ?Q44) DEFINE CLUSTER(cluster name) with the INDEXED parameter. Also specify the ds name for the DATA component & the ds INDEX component. Other important parms are RECORDSIZE, KEYS, SHAREOPTIONS.
Q45) How do you define an ALTINDX ? How do you use ALTINDXs in batch, CICS pgm’s ?Q45) DEFINE ALTERNATEINDEX. Important paramters are RELATE where you specify the base cluster name, KEYS, RECORDSIZE,SHAREOPTIONS,UNIQUEKEY(or NONUNIQUEKEY), DATA(ds name for the data component), INDEX(ds name for the index component). Then DEFINE PATH. Important paramters are NAME (ds name for the path), PATHENTRY (ds name of the alternate index name), UPDATE(or NOUPDATE) which specifies whether an alt index is updated when a update to the base cluster takes place. Then BLDINDEX. Parameters are INDATASET(ds name of base cluster), OUTDATASET(ds name of AIX).
Q46) Using Alternate Indexes in Batch pgms:Q46) In the JCL, you must have DD stmts for the cluster and for the path(s). In the COBOL Program, SELECT .. ASSIGN TO ddname for base cluster RECORD KEY IS... ALTERNATE RECORD KEY IS..
Q47) Using Alternate Indexes in CICS pgms:Q47) FCT entries must be created for both base cluster & the path. To read using the alternate index, use the dd name of the path in CICS file control commands.
Q48) What happens when you open an empty VSAM file in a COBOL program for input?Q48) A VSAM file that has never contained a record is treated as unavailable. Attempting to open for input will fail. An empty file can be opened for output only. When you open for output, COBOL will write a dummy record to the file & then delete it out.
Q49) How do you initialize a VSAM file before any operation? a VSAM with alternate index?Q49) Can write a dummy program that just opens the file for output and then closes it.
Q50) What does a file status of 02 on a VSAM indicate?Q50) Duplicate alternate key . Happens on both input and output operation
Virtual Storage Access Method (VSAM)
Q1) What are the types of VSAM datasets?A1) Entry sequenced datasets (ESDS), key sequenced datasets (KSDS) and relative record dataset (RRDS).
Q2) How are records stored in an ESDS, entry sequenced dataset?A5) They are stored without respect to the contents of the records and in the order in which they are included in the file.
Q3) What is a CI, control interval?A3) A control interval is the unit of information that VSAM transfers between virtual and auxiliary storage.
Q4) What are the distinctive features of a ksds, key sequenced dataset?A4) The index and the distributed free space.
Q5) What is a CA, control area?A5) A group of control intervals makes up a control area.
Q6) What is a sequence set?A6) This is the part of the index that points to the CA and CI of the record being accessed.
Q7) What is the index set?A7) This is the other part of the index. It has multiple levels with pointers that ultimately reach to the sequence set.
Q8) What is a cluster?A8) A cluster is the combination of the index, sequence set and data portions of the dataset. The operating system gives program access to the cluster, ie. to all parts of the dataset simultaneously.
Q9) What is the catalog?Q9) The catalog contains the names of all datasets, VSAM and non-VSAM. It is used to access these datasets.
Q10) What is an alternate index?Q10) An AIX is a file that allows access to a VSAM dataset by a key other than the primary one.
Q11) What is a path?Q11) A path is a file that allows you to access a file by alternate index - the path provides an association between the AIX and the base cluster.
Q12) What is the upgrade set?Q12) The upgrade set is the list of all AIXes that VSAM must maintain for a specific base cluster, so that when data in the base cluster is updated, the AIX files are also updated.
Q13) What is free space?Q13) Free space is reserved within the data component of a KSDS to accommodate inserting new records.
Q14) What is a VSAM split?Q14) If there isn't enough space in the control interval VSAM performs a control interval split by moving some records to the free control intervals. If there isn't a free control interval VSAM performs a control area split by allocating a new control area and moving half of the control intervals to it.
Q15) What is the base cluster?Q15) The base cluster consists of the data component and the index component for the primary index of a KSDS.
Q16) Do primary key values have to be unique? Do alternate key values have to be unique?Q16) Primary key values must be unique; alternate key values need not be.
Q17) In the COBOL SELECT statement what is the ORGANIZATION for a KSDS?Q17) The ORGANIZATION is INDEXED.
Q18) In the COBOL SELECT statement for a KSDS what are the three possibilities for ACCESS?Q18) ACCESS can be SEQUENTIAL, RANDOM or DYNAMIC.
Q19) What is the COBOL RECORD KEY clause?Q19) The RECORD KEY in the SELECT clause identifies the files primary key as it will be known to the program.
Q20) What is the purpose of the FILE STATUS clause in the SELECT statement?Q20) The FILE STATUS field identifies the field that VSAM uses to provide information about each I/O operation for the file.
Q21) If you wish to use the REWRITE command haw must the VSAM file be opened?Q21) It must be opened as I/O.
Q22) Explain the meaning and syntax for the START command.Q22) The START command is used read other than the next VSAM record. A value must be moved into the RECORD KEY. The KEY clause is optional, but it can be used to specify a relational (equal, less than, etc.) operator.
Q23) What is the meaning of dynamic processing?Q23) It's rarely used. It means one program uses both sequential and random processing for a VSAM KSDS file.
Q24) Name some common VSAM error conditions and codes.Q24) They are end of file (10), duplicate key (22), record not found (23), VSAM logic error (90), open problem (92) and space problem (93).
Q25) What is the VSAM-code field?Q25) It is a COBOL II enhancement to VSAM batch processing expanding the FILE STATUS field. It is defined in WORKING-STORAGE as a six byte group item with three two byte elements, the normal return code, the function code and the feedback code.
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