Knowledge Base : Shared pool reserved pct

percentage memory of the shared pool allocated for the reserved area to Shared Pool fragmentation can be minimized and ORA-4031 reduced by setting

_shared_pool_reserved_pct 5

The memory pool in the SGA are comprised of memory chunks in various sizes. When the database starts is started, you have a large chunk of memory allocated in the various pools and tracked in free list hash buckets. Over time, as memory is allocated and deallocated, the memory chunks are moved around into different free list buckets inside the pool according to their size. An ORA-04031 error occurs in any of the memory pools in the SGA when Oracle cannot find a memory chunk large enough to satisfy an internal allocation request on behalf of a user’s operation.