If a cache is dedicated to a table or an index, and the cache has little or no buffer replacement when the system reaches a stable state, you can set the relaxed LRU (least recently used) replacement policy. The relaxed LRU replacement policy can improve performance for caches where there is little or no buffer replacement occurring, and for most log caches. See Chapter 5, “Memory Use and Performance” in the Performance and Tuning Series: Basics for more information.
To set relaxed replacement policy, use:
sp_cacheconfig pubs_log, relaxed
The default value is “strict.”
Setting the cache replacement policy is not dynamic
and requires a restart of Adaptive Server to take effect.
You can create a cache and specify its cache type and the replacement policy in one command. These examples create two caches, pubs_log and pubs_cache:
sp_cacheconfig pubs_log, "3M", logonly, relaxed
sp_cacheconfig pubs_cache, "10M", mixed, strict
The change takes place immediately and is made to every cache partition of the named cache.
Here are the results:
sp_cacheconfig
Cache Name Status Type Config Value Run Value ------------------------ --------- -------- ------------ ------------ default data cache Active Default 25.00 Mb 42.29 Mb pubs_cache Active Mixed 10.00 Mb 10.00 Mb pubs_log Active Log Only 7.00 Mb 7.00 Mb ------------ ------------ Total 42.00 Mb 59.29 Mb ======================================================================= Cache: default data cache, Status: Active, Type: Default Config Size: 25.00 Mb, Run Size: 42.29 Mb Config Replacement: strict LRU, Run Replacement: strict LRU Config Partition: 1, Run Partition: 1 IO Size Wash Size Config Size Run Size APF Percent -------- --------- ------------ ------------ ----------- 2 Kb 8662 Kb 0.00 Mb 42.29 Mb 10 ======================================================================= Cache: pubs_cache, Status: Active, Type: Mixed Config Size: 10.00 Mb, Run Size: 10.00 Mb Config Replacement: strict LRU, Run Replacement: strict LRU Config Partition: 1, Run Partition: 1 IO Size Wash Size Config Size Run Size APF Percent -------- --------- ------------ ------------ ----------- 2 Kb 2048 Kb 0.00 Mb 10.00 Mb 10 ======================================================================= Cache: pubs_log, Status: Active, Type: Log Only Config Size: 7.00 Mb, Run Size: 7.00 Mb Config Replacement: relaxed LRU, Run Replacement: relaxed LRU Config Partition: 1, Run Partition: 1 IO Size Wash Size Config Size Run Size APF Percent -------- --------- ------------ ------------ ----------- 2 Kb 1432 Kb 0.00 Mb 7.00 Mb 10
