Prefetchers view shows the usage and performance of prefetchers.

The purpose of prefetching system is to retrieve data from physical storage to have it available at the time it is required by tasks running in the database. It depends on prefetchers to read data from the I/O subsystem.

The buffer pool identifier for the buffer pool that is being monitored.

Source: MON_GET_BUFFERPOOL(”, #MEMBER#).BP_NAME

The percentage of pages which have been asynchronously read from the table space containers (physical).

= ASYNC_READS / P_READS

Source:

ASYNC_READS = MON_GET_BUFFERPOOL(”, #MEMBER#).(SUM(POOL_ASYNC_DATA_READS) + SUM(POOL_ASYNC_INDEX_READS) + SUM(POOL_ASYNC_XDA_READS) + SUM(POOL_ASYNC_COL_READS))

P_READS = MON_GET_BUFFERPOOL(”, #MEMBER#).(SUM(POOL_DATA_P_READS) + SUM(POOL_INDEX_P_READS) + SUM(POOL_XDA_P_READS) + SUM(POOL_COL_P_READS) + SUM(POOL_TEMP_DATA_P_READS) + SUM(POOL_TEMP_INDEX_P_READS) + SUM(POOL_TEMP_XDA_P_READS) + SUM(POOL_TEMP_COL_P_READS))

The percentage of times a page was physically written to disk by either an asynchronous page cleaner, or a prefetcher.

= ASYNC_WRITES / POOL_WRITES

Source:

ASYNC_WRITES = MON_GET_BUFFERPOOL(”, #MEMBER#).(SUM(POOL_ASYNC_DATA_WRITES) + SUM(POOL_ASYNC_INDEX_WRITES) + SUM(POOL_ASYNC_XDA_WRITES) + SUM(POOL_ASYNC_COL_WRITES))

POOL_WRITES = MON_GET_BUFFERPOOL(”, #MEMBER#).(SUM(POOL_DATA_WRITES) + SUM(POOL_INDEX_WRITES) + SUM(POOL_XDA_WRITES) + SUM(POOL_COL_WRITES))

The number of pages read in from the table space containers (physical).

Source: MON_GET_BUFFERPOOL(NULL, #MEMBER#).(SUM(POOL_DATA_P_READS) + SUM(POOL_INDEX_P_READS) + SUM(POOL_XDA_P_READS) + SUM(POOL_COL_P_READS) + SUM(POOL_TEMP_DATA_P_READS) + SUM(POOL_TEMP_INDEX_P_READS) + SUM(POOL_TEMP_XDA_P_READS) + SUM(POOL_TEMP_COL_P_READS))

The number of pages which have been asynchronously read from the table space containers (physical).

Source: MON_GET_BUFFERPOOL(”, #MEMBER#).(SUM(POOL_ASYNC_DATA_READS) + SUM(POOL_ASYNC_INDEX_READS) + SUM(POOL_ASYNC_XDA_READS) + SUM(POOL_ASYNC_COL_READS))

The average time an application spent waiting for an I/O server (prefetcher) to finish loading pages into the buffer pool.

= PREFETCH_WAIT_TIME / PREFETCH_WAITS

Source:

PREFETCH_WAIT_TIME = MON_GET_BUFFERPOOL(”, #MEMBER#).SUM(PREFETCH_WAIT_TIME)

PREFETCH_WAITS = MON_GET_BUFFERPOOL(”, #MEMBER#).SUM(PREFETCH_WAITS)

The number of pages that the prefetcher read into the bufferpool that were never used.

Source: MON_GET_BUFFERPOOL(”, #MEMBER#).SUM(UNREAD_PREFETCH_PAGES)