Library Cache Hit Ratio

The library cache (a component of the shared pool) stores the executable (parsed or compiled) form of recently referenced SQL and PL/SQL code. Oracle tries to reuse this code.

• If the code has been executed previously and can be shared, Oracle will report a library cache hit.
• If Oracle is unable to use existing code, then a new executable version of the code must be built, which is known as a library cache miss.