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mijanurit Currently Banned New User
Joined: 26 Aug 2005 Posts: 33 Location: bangalore
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What is VSAM reorganisation and how frequently we need to do it?
Rahman |
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Robert Sample
Global Moderator
Joined: 06 Jun 2008 Posts: 8697 Location: Dubuque, Iowa, USA
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You reorganize a VSAM file by unloading the data from it, deleting, defining, and reloading the data into it. This is done to remove CI/CA splits, which slow down data access. As to how frequently you need to do it, that depends entirely upon the circumstances. A file that has no CI/CA splits isn't going to benefit from a reorganization. A file that splits hundreds or thousands of times a day probably needs a reorganization every night. You have to balance the resources required to reorganize the file versus the additional access required by a file with splits. |
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Garry Carroll
Senior Member
Joined: 08 May 2006 Posts: 1193 Location: Dublin, Ireland
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Where a file is getting a high level of CI/CA splits, consideration should be given to adjusting the FREESPACE values. Be aware that the CA freespace should likely be a lower percentage than CI freespace. This is because the freespace is cumulative - i.e. given 100 cyls, CA FSPC of 20 leave 80% available for CIs (80Cyl). If CI FSPC is also 20, then only 80% of that remaining space is available (64Cyl) for initial load of data. Overall, that means 36% of the data area is unused after re-organisation.
CA split only occurs where a CI split requires use of another CA, so these are less frequent than CI splits.
Garry. |
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