Data cache hitrate 
Data cache hitrate <percentage>%, <number> of <number> accesses failed
Explanation
The
hit rate when accessing the 
data cache is too
low. In a running liveCache
application, the hit rate should not be under 100%.
Lower
hit rates may occur for short periods of time, for example, when objects are
accessed for the first time, or if a table that is being scanned (TABLE SCAN)
is larger than 10% of the data cache (only if the database parameter LRU_FOR_SCAN has
the value
yes). Data
cache hit rates that are lower than 99% over 15 minutes must be
avoided.
User Response
Check the following points:
- Load in the data cache
- Configuration of the database instance and the hardware
-
In liveCache instances, the
size of the plan versions, as well as OMS versions that
have existed for a long time.
Individual SQL statements can often take up a large proportion of the total logical and physical reads. Increasing the cache just moves the load from the hard disk to the CPU, even though, for example, an additional index could turn a read-intensive table scan into quick direct access.
For
information on creating optimized SQL statements, see Optimizer:
SAP DB 7.4.