IDMS: Logically full database pages
Article ID: 24141
Updated On:
Products
Issue/Introduction
The PRINT SPACE utility report shows an area with Total Space Available of 0% but also 30% Total Space Unusable and Total Unreserved Space Available.
What does this mean?
Environment
Release: All supported releases.
Cause
The Total Space Available is taking into account pages that are logically full. If PRINT SPACE is run with the FULL option, it will list the number of pages that are logically full.
Total Unreserved Space Available is the space not used by records but does not take into account logically full pages.
Total Space Unusable is the amount of space that is unavailable because of logically full pages.
For a standard radix dbkey, IDMS can fit 255 records on a page. This is the maximum limit for a standard dbkey. The dbkey radix represents the number of bits within a dbkey value that are reserved for the line number of a record. By default, this value is 8, meaning that up to 255 records can be stored on a single page of the area.
Though there may be space on each page, there are only 255 (2 ** 8 - 1) line indexes available for use, so regardless of the sizes of the pages and the records, there can never be more than 255 records on such a page. In this case, the page is considered logically full.
For example, if a record size is 80 bytes, storing 255 records on a page would result in the usage of 20,400 bytes.
If the page size is 28,000, there will be 7,600 bytes not usable on each page of the area.
Resolution
In this situation, run an Unload/Reload, specifying a smaller page size and larger page range to better fit all the records.
Additional Information
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