Catalog cache hitrate (SQL Pages) <percentage>%, <number> of <number> accesses failed
The hit rate is too low when accessing the catalog cache in which the parsed SQL statements are administered. In a running database application, the catalog cache hit rate should be about 90%. If new program components or programs are started, the hit rate can drop temporarily to a low level. However, the average over a 15-minute period should not drop below 85%. ==> raus
The hit ratio is too low when accessing the catalog cache. Since Shared SQL is used the catalog cache lost importance. Catalog information is still kept in the catalog cache but the parse information for commands are now kept in Shared SQL cache. Thus a lower hit ratio is usually not very critical. Nevertheless, if a lot of accesses to the catalog are required, the hit ratio should not drop under a certain level.
The size of the catalog cache should be about 100 pages for each database session. You can check this using the parameter MaxUserTasks and the TaskSpecificCatalogCacheMinSize. ==> gilt diese Empfehlung so noch?
The catalog cache is enlarged dynamically by the active database sessions, and released again with a RELEASE statement. You can determine the current cache sizes using the SQL statement SELECT * FROM CONNECTEDUSERS. ==> raus
If sessions need significantly more than 100 pages, we recommend that in the medium term you increase the catalog cache accordingly, memory permitting.
Relevant DB-Analyzer Files
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|DBAN_CATALOG_CACHE.csv||Counts successful and unsuccessful accesses to catalog cache, and also hit rate|
Expert Sessions (Link to trainings)
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|Documentation (Links)||Helpful with ...|