Fresh Virtual storage access method (VSAM) Interview Preparation Guide

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No, they would not be left empty. one record will be written in each CI and 1 CI will be written for each CA.

The Index and data components of a KSDS

The answer is : 1

122 TIMES

By USING RBA (Relative Byte Address).

FREE SPACE ( FPSC )

2 data buffers by default for ESDS. For KSDS it allots 2 data buffers and 1 index buffers. each buffer is about 4K.

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.

No delete operation is not possible in VSAM ESDS.B. yes rewrite operation is possible in an ESDS.

There two datasets are VSAM datasets. ESDS maintains control information. But LDS does not maintains the control information.

Using IDCAMS a member can be deleted. DELETE 'XXX.YYY (memeber)

IDCAMS is an access method services utility used for creating, deleting, altering VSAM files and coping sequential file to a VSAM file, etc.

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 begin copying at 9001 and copies 700 records from DD1 to DD2.

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 inprovement.

It define 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 defualt is SHR(1 3).

RECOVERY (default ) and SPEED are mutually exclusive. Recovery performats the control areas during the initial dataset load, if the job fails, you can restatt 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.

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.

255 - but you must be a nut to have so many ALT Indexes on a dataset !

only on KSDS and ESDS - not RROS

Out of space condition is raised.

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 datset.
Use IDCAMS to ALTER / rename the new VSAM dataset to the name of the original VSAM dataset.

Run VERIFY.

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.

base-file-name. GnnnnnnV00 where nnnn=generation number (upto 255). nnnn will be 0000 for the 1st generation.

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)