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Snapshot Level Database Application |
Logical Data Grouping dbase appl |
Monitor Switch Basic Basic |
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Resettable |
Yes |
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Event Type Database Connection |
Logical Data Grouping db_event conn_event |
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Element Name Element Type |
cat_cache_lookups counter |
Description: The number of times that the catalog cache was referenced to obtain table descriptor information.
Usage: This element includes both successful and unsuccessful accesses to the catalog cache. The catalog cache is referenced whenever a table, view, or alias name is processed during the compilation of an SQL statement.
To calculate the catalog cache hit ratio use the following formula:
(1 - (cat_cache_inserts / cat_cache_lookups))
indicates how well the catalog cache is avoiding catalog accesses. If the ratio is high (more than 0.8), then the cache is performing well. A smaller ratio might suggest that the catalogcache_sz should be increased. You should expect a large ratio immediately following the first connection to the database.
The execution of Data Definition Language (DDL) SQL statements involving a table, view, or alias will evict the table descriptor information for that object from the catalog cache causing it to be re-inserted on the next reference. Therefore, the heavy use of DDLs may also increase the ratio.
See the Administration Guide for more information on the Catalog Cache Size configuration parameter.