Library CachePct Misses should be very low. If they exceed 10%, your SQL
statements may use unsharable SQL. You can fix this by either using bind
variables or by the
ALTER SYSTEM to
change its value without restarting the instance.
An important statistic to look at is the number or RELOADS. If there are significant number of RELOADS, then reusable information is being aged out of the SGA, and hence having to be reloaded and rebuilt. This indicates the shared pool may need attention (which may include resizing, changing large pool, pinning objects etc). Also look for a high number of invalidations. An invalidation occurs when an object in the library cache is determined to be no longer valid for execution or reference; this housekeeping is done automatically by Oracle. One situation where objects are invalidated is when executing DDL operations frequently. The effects of invalidations can be reduced by executing DDL statements during off peak periods. |