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[GuruRaj]

hi
can any one tell me how to compress a volume and compress vsam dataset.

[Mike Chantrey]

1/ Compress volume: There are various utilities for doing this but it would normally be done either as routine or when required, by your storage admin group (e.g. the people you would go to if you needed more DASD space etc.). Doing it yourself without fully understanding what you are doing could cause all sorts of trouble (e.g. I believe some products can move datasets which are 'in use' unless you tell them not to, this could cause an online system to crash, for example).

2/ Compress VSAM dataset: I guess you are referring to a reorganization (reorg) which will defragment a VSAM file with lots of CI/CA splits. This is typically done using IDCAMS (see 'DFHSMS access method services' manual) to create/copy/rename a new file. The steps involve the concept of a current file (the file you want to compress), a .OLD file and a .NEW file:
a/ Use DELETE CLUSTER to delete 'vsamfile.OLD' from previous compress
b/ Use DEFINE CLUSTER with MODEL to create a 'vsamfile.NEW' modelled on the current file
c/ Use REPRO to copy current file to .NEW file.
d/ Use ALTER to rename each of the 3 components (base,index,data) of the current file to .OLD
e/ Use ALTER to rename each of the 3 components (base,index,data) of the .NEW file to become the 'current' file.

Steps a/,b/, and c/ can be done in a single IDCAMS JCL step; then do steps d/ and e/ in a second IDCAMS step which should only be run if the previous step suceeds. This means the reorg will 'fail safe' - if the new file fails to be created for any reason the renames will not occur and you will still have a working 'current' file.

If you want to do this process 'manually' as a one-off, you can use FILEAID to perform equivalent operations very easily if you have this product.

[Mike Chantrey]

Here's a sample REORG for file MYNODE.TESTVSAM: