Decreasing the Size of a Cache

When you reduce the size of a cache, you must restart SAP ASE for the change to take effect.

This is a report on the pubs_log cache:

sp_cacheconfig pubs_log

Cache Name               Status    Type     Config Value Run Value
------------------------ --------- -------- ------------ ------------
pubs_log                 Active    Log Only      7.00 Mb      7.00 Mb
                                            ------------ ------------
                                     Total       7.00 Mb      7.00 Mb
=======================================================================
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    920 Kb      0.00 Mb      4.50 Mb     10
    4 Kb    512 Kb      2.50 Mb      2.50 Mb     10

The following command reduces the size of the pubs_log cache to 6MB from a current size of 7MB:

sp_cacheconfig pubs_log, "6M"

After a restart of SAP ASE, sp_cacheconfig shows:

Cache Name               Status    Type     Config Value Run Value
------------------------ --------- -------- ------------ ------------
pubs_log                 Active    Log Only      6.00 Mb      6.00 Mb
                                            ------------ ------------
                                     Total       6.00 Mb      6.00 Mb
=======================================================================
Cache: pubs_log,   Status: Active,   Type: Log Only
     Config Size: 6.00 Mb,   Run Size: 6.00 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    716 Kb      0.00 Mb      3.50 Mb     10
    4 Kb    512 Kb      2.50 Mb      2.50 Mb     10

When you reduce the size of a data cache, all the space to be removed must be available in the default pool (which is the smallest size available). You may need to move space to the default pool from other pools before you can reduce the size of the data cache. In the last example, to reduce the size of the cache to 3MB, use sp_poolconfig to move some memory into the default pool of 2K from the 4K pool. The memory is moved to “memory available for named caches.”