The options to expand an IDMS database area
Article ID: 117673
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Issue/Introduction
What different choices are there for increasing the size of an IDMS database area?
Environment
Release: All supported releases.
Resolution
There are three choices.
The best choice is also the one that involves the most work and time. This is to unload and reload the records in the area based on a new definition of the area that has a greater number of pages. This can be done using the UNLOAD/RELOAD utility or the newer REORG utility, both documented in the Utilities Guide.
What are the steps to run a basic unload-reload?
Second best choice is EXPAND PAGE utility which keeps the same number of pages in the area but increases the Page Size. This choice does not do any record level access so no re-clustering or re-organizing is done. It simply adds more space on each page to contain more records. Depending on the current page size or the size of the records that will be stored on those pages, this choice may not provide the additional space needed. The page size may already be large and the page size may have originally been calculated to be the optimal size for the records being stored in the area. Every database SEGMENT has a clause that indicates the maximum number of records per page. The default is 255. So if the pages in the area are already near 255 records per page, increasing page size will not help much, or at all.
The third choice is an EXTEND SPACE modification to the AREA definition, which allows you to add an additional FILE to the area, but again no reorganization of records/clusters is done and the additional file is only available for overflow. NOTE: If this is done it should be considered an emergency operation and very temporary. Unload/Reload or REORG should be scheduled as soon as possible to reload all records into the larger area using a definition that includes the new file as primary space.
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