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.

Q1) Difference between KSDS and ESDS- KSDS record can be accessed by primary key. ESDS record can be accessed randomly with displacement address(RBA)

Q2) AMS stands for access method services. It is used to create and maintain datasets

Q3) SHAREOPTIONS- It states how the file will be shared between jobs, batch and CICS

Q4)//Trans DD Dummy, AMP=’AMORG’- This refers to vsam dataset

Q5) DD name for ESDS must be prefixed with “AS-”
//AS-TRANS  DD DSN=xyz

Q6) ESDS extensively used in online CICS. Since CICS can get access to record through “RBA”

Q7) ESDS can not be used as GDG.

Q8) Indexed- KSDS, Nonindexed-ESDS, Numbered-RRDS. Out of these “Indexed ” is default parameter.

Q9) CA/CI level spilts causes performance degradation. If splits are more it causes more I/O, and reduce the performance.

Q10) Verify command close the file correctly. Sample code

//SYSIN DD *

PRINT INDATASET(SYS1.VVDS.V339000) DUMP

ALTER DFP1.JIMONE.KSDS.DATA UNINHIBIT

ALTER DFP1.JIMONE.KSDS.INDEX UNINHIBIT

VERIFY DATASET(DFP1.JIMONE.KSDS)

LISTC ENT(DFP1.JIMONE.KSDS) ALL

/*

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.