Prefetch access paths (PREFETCH='D', 'S', 'L', or 'U')

Prefetch is a mechanism for reading a set of pages into the buffer pool with only one asynchronous I/O operation.

Prefetch can allow substantial savings in both CPU and I/O by avoiding costly synchronous read I/O operations. To achieve those savings, you can monitor the use of prefetch, and take steps to enable your queries to take advantage of optimal prefetch access paths.

DB2® uses a process called sequential detection to determine whether to use prefetch and the type of prefetch to use. DB2 uses different types of prefetch in different situations, including dynamic prefetch, sequential prefetch, and list prefetch.