Data cache hitrate <percentage>%, <number> of <number> accesses failed
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 repeatedly (TABLE SCAN) is larger than 10% of the data cache (only if the special database parameter LRU_FOR_SCAN has the value yes). Data cache hit rates that are lower than 99% over a fifteen minute average must be avoided.
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 a quick direct access. For information on creating optimized SQL statements, see the SQL Optimizer section.