In-memory buffer pools

In Db2 12, you can assign objects to in-memory buffer pools. The data pages for the object remain in the buffer pool if they can fit within the size of the buffer pool.

By assigning frequently accessed objects to in-memory buffer pools, you can reduce the cost of internal processing and I/O for those objects.

In-memory buffer pools are created by the PGSTEAL(NONE) option of the ALTER BUFFERPOOL command. Db2 implicitly creates an overflow area as part of the bufferpool. Objects that cannot fit within the in-memory part of the buffer pool are allocated to the overflow area. Page stealing can occur in the overflow area. LRU chains are maintained for the overflow area, but buffer stealing in the overflow area uses the FIFO page-stealing algorithm. When you specify PGSTEAL(NONE), it is best to specify a buffer pool size that is large enough to contain all assigned objects that might be open at the same time. Pages that are allocated to the overflow area cannot be returned to the main area of the bufferpool until the object is closed.

Db2 issues a console message whenever an object is allocated to the overflow area for in-memory buffer pool.