Adjusting HDAM and PHDAM options

You can choose from a number of different HDAM and PHDAM options, each of which have performance implications.

1. Determine whether the change you are making will affect the code in any application programs. It should only do so if you are changing to a sequential randomizing module.
2. Unload your database, using the existing DBD and the appropriate unload utility.
3. Code a new DBD (for non-PHDAM) using the TSO Partition Definition Utility.
   If you changed your CI or block size, you need to allocate buffers for the new size.
4. If the change you are making affected the code in application programs, make any necessary changes to the PSBs for those application programs. If you have the DB/DC Data Dictionary, it can help you determine which application programs and PCBs are affected by the DBD changes you have made.
5. Determine whether you need to recalculate database space.
6. For non-VSAM data sets, delete the old database space and define new database space. For VSAM data sets, delete the space allocated for the old clusters and define space for the new clusters.
7. Reload your database or partition using the new DBD (if any) and the appropriate reload utility. Make an image copy of your database as soon as it is reloaded.