Display the cache hit rate.
Messaging Server 7.0: Run the imcheck -s mpool command.
Messaging Server 6.3: Run the imcheck -s command.
Messaging Server 6.2: Run the db_stat command as follows. In this example, the configutil parameter store.dbtmpdir has redefined the location of the mailbox database to /tmp, that is, /tmp/mboxlist.
# /opt/SUNWmsgsr/lib/db_stat -m -h /tmp/mboxlist
2MB 513KB 604B Total cache size. 1 Number of caches. 2MB 520KB Pool individual cache size. 0 Requested pages mapped into the process’ address space. 55339 Requested pages found in the cache (99%).
Examine the cache hit rate.
In this case, the hit rate is 99 percent. This could be optimal or, more likely, it could be that the cache is too large. To test, lower the cache size until the hit rate moves to below 99 percent. When you hit 98 percent, you have optimized the DB cache size. Conversely, if see a hit rate of less than 95 percent, then you should increase the cache size with the store.dbcachesize parameter. The maximum size is the total of all the *.db files in the store/mboxlist directory. The cache size should not exceed the total size of all of the .db files under the store/mboxlist directory.
As your user base changes, the hit rate can also change. Periodically check and adjust this parameter as necessary.
This parameter has an upper limit of 2 GB imposed by the database.