VSAM Tough Questions (1 of 2)

I am just giving my stack on VSAM, since VSAm is extensively being used in CICS. It is popular access method. All database DB2/IMSDB underlying datasets are still VSAM.

  1. Main difference between KSDS and ESDS?
    1. KSDS record can be accessed by primary key. ESDS record can be accessed randomly with displacement address(RBA)
  2. What is AMS in VSAM?
    1. AMS stands for access method services. It is used to create and maintain datasets
  3. What is SHAREOPTIONS?
    1. It states how the file will be shared between jobs, batch and CICS
  4. What is //Trans DD Dummy, AMP=’AMORG’?
    1. This refers to vsam dataset
  5. DD name for ESDS must be prefixed with “AS-“?
    1. //AS-TRANS  DD DSN=xyz
  6. Why ESDS used in CICS?
    1. ESDS extensively used in online CICS. Since CICS can get access to record through “RBA”
  7. Do we need to use ESDS as GDG?
    1. ESDS can not be used as GDG.
  8. What is default?
    1. Indexed- KSDS, Nonindexed-ESDS, Numbered-RRDS. Out of these “Indexed ” is default parameter.
  9. What is CA/CI level split?
    1. CA/CI level spilts causes performance degradation. If splits are more it causes more I/O, and reduce the performance.
  10. What is verify?
    1.  Verify command close the file correctly. Sample code
      1. //SYSIN DD *
      2. PRINT INDATASET(SYS1.VVDS.V339000) DUMP
      3. ALTER DFP1.JIMONE.KSDS.DATA UNINHIBIT
      4. ALTER DFP1.JIMONE.KSDS.INDEX UNINHIBIT
      5. VERIFY DATASET(DFP1.JIMONE.KSDS)
      6. LISTC ENT(DFP1.JIMONE.KSDS) ALL
      7. /*

Bye… wait for my next stack on VSAM.

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Author: Srini

Experienced software developer. Skills in Development, Coding, Testing and Debugging. Good Data analytic skills (Data Warehousing and BI). Also skills in Mainframe.