VSAM Interview Questions

31. What is the meaning of the DEFINE MODEL parameter?
It specifies whether Daniela Pestova or Yamila - oops! Wrong models! The MODEL parameter allows you to model your cluster by modelling it after an existing cluster.

32. How do you fix the problem associated with VSAM out of space condition?
1. Define new VSAM dataset allocated with more space. 2. Use IDCAMS to REPRO the old VSAM file to new VSAM dataset. 3. Use IDCAMS to ALTER / rename the old VSAM dataset or se IDCAMS to DELETE the old VSAM dataset. 4. Use IDCAMS to ALTER / rename the new VSAM dataset to the name of the original VSAM dataset.

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

34. Correction to the previous question - Yor can have ALT INDEX only onKSDS and ESDS - not RRDS.
See the question for correction - you cannot have ALT INDEX for RRDS.

35. How amny Alternate Indexes you can have on a dataset? - Remember ALT INDEX is possibleonly on KSDS and RRDS.
255 - but you must be a not to have so many ALT Indexes on a dataset!

36. 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.

37. What is RECOVERY and SPEED parameters in DEFINE CLUSTER command?
RECOVERY (default) and SPEED are mutulally 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.

38. Describe SHAREOPTIONS parameter (SHR) in Define Cluster command.
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).

39. What does the KEYRANGES parmater in Define Cluster commend do?
It divides a large dataset into several volumes accoring to the Keyranges specified. e.g., KEYRANGES ((0000001 2999999) (3000000 5999999)). if the activity on the key ranges are evenly distributed, cuncurrent access is possible, which is aperformance improvement.

40. What is GDG means in VSAM?
Generation Data Group

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