Filter cache

 

When the client issues a query for data and the query cannot be resolved in memory by the attribute cache manager, the query goes to the filter cache. This cache contains cached entry IDs.

There are two things that can happen when a query arrives at the filter cache:

• The IDs that match the filter settings used in the query are located in the filter cache. If this is the case, the list of the matching entry IDs is sent to the entry cache.

• The matching entry IDs are not cached in the filter cache. In this case, the query must access DB2 in search of the desired data.

To determine how big your filter cache should be, run your workload with the filter cache set to different values and measure the differences in operations per second.

The filter cache bypass limit configuration variable limits the number of entries that can be added to the filter cache. For example, if the bypass limit variable is set to 1,000, search filters that match more than 1,000 entries are not added to the filter cache. This prevents large, uncommon searches from overwriting useful cache entries. To determine the best filter cache bypass limit for your workload, run your workload repeatedly and measure the throughput.

 

Parent topic:

Server caches