Wednesday, 28 January 2015

VSAM Interview Questions and Answers Part2

11. How to delete a member using JCL?
Using IDCAMS a member can be deleted. DELETE 'XXX.YYY (memeber)

12. What is IDCAMS? and what is the purpose of it?
IDCAMS is an access method services utility used for creating, deleting, altering VSAM files and coping sequential file to a VSAM file, etc.

13. What are the optional parameters to the input dataset While loading the empty cluster with the data records?
1) FROMADDRESS(address)
2) TOADDRESS(address) where 'address' specifies the RBA value of the key of the input record.
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.

14. What does the KEYRANGES parameter in Define Cluster commends do?
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.

15. Describe SHAREOPTIONS parameter (SHR) in Define Cluster command?
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).

16. What is RECOVERY and SPEED parameters in DEFINE CLUSTER command?
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.

17. Is it slower if you access a record through ALT INDEX as compared to Primary INDEX?
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.

18. How many ALternate Indexes you can have on a dataset?
255 - but you must be a nut to have so many ALT Indexes on a dataset !

19. On which dataset You can have ALT INDEX?
only on KSDS and ESDS - not RROS

20. What is the meaning of VSAM RETURN-CODE 28?
Out of space condition is raised.

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