Caches 
In the Memory Areas user menu you can see, among other things, the sizes of the most important caches, the number of accesses to these caches, and the cache hit rates since the last time the Database Monitoring function was started.
Procedure
Open the Database Assistant (transaction DB50) or the liveCache Assistant (transaction LC10). Choose 
Current Status 
Memory Areas Caches 
.
or
Open the DBA Cockpit (transaction DBACOCKPIT) and select Space Caches .
Result
The system displays information about the size and general efficiency of the caches of the database instance. In a balanced system, the hit rate for the data cache is more than 99 %, for the catalog cache more than 90 %. The lower the hit rate, the lower the efficiency of your database system.
Cache sizes | Size of the I/O buffer cache, the data cache and other caches (in 8 KB pages) |
Cache accesses | Statistical information about accesses to the data cache; information for the liveCache includes accesses to the OMS data, SQL data and links to undo log entries for the objects. |
Cache-specific parameter settings | CACHE_SIZE: Size of the I/O buffer cache CAT_CACHE_SUPPLY: Size of the catalog cache |
The I/O buffer cache (with its main component, the data cache) should be configured large enough that the greatest possible amount of data you require for normal operation of your SAP system can be stored in the data cache. Otherwise, the data is written to the data area, which negatively affects database performance. If necessary, change the size of the I/O buffer cache by setting the general database parameter CACHE_SIZE.
For SAP systems with special requirements, a higher data cache hit rate may also be necessary (such as SAP NetWeaver BI).
Comments About liveCache
The I/O buffer cache, and therefore the data cache as well, must be dimensioned so that it can hold all OMS data, links to undo log entries, and SQL data in the data cache. Otherwise, the data is written to the data area, which negatively affects liveCache performance.
The memory of the data cache should take up about 40% of the main memory available to the liveCache database instance. You may need to adjust its size to the requirements of the application.
See also: Monitoring the Main Memory Areas
More Information
Database Alert Monitor: Caches
liveCache Alert Monitor, Caches, Memory
Concepts of the Database System, Monitoring, General Database Parameters,Special Database Parameters