DB2 Version 9.7 for Linux, UNIX, and Windows

pool_drty_pg_thrsh_clns - Buffer pool threshold cleaners triggered monitor element

The number of times a page cleaner was invoked because a buffer pool had reached the dirty page threshold criterion for the database.

Table 1. Table Function Monitoring Information
Table Function	Monitor Element Collection Command and Level
MON_GET_BUFFERPOOL table function - Get buffer pool metrics	DATA OBJECT METRICS BASE

Table 2. Snapshot Monitoring Information
Snapshot Level	Logical Data Grouping	Monitor Switch
Database	dbase	Buffer Pool

For snapshot monitoring, this counter can be reset.

Table 3. Event Monitoring Information
Event Type	Logical Data Grouping	Monitor Switch
Database	event_db	-

Usage

The threshold is set by the chngpgs_thresh configuration parameter. It is a percentage applied to the buffer pool size. When the number of dirty pages in the pool exceeds this value, the cleaners are triggered.

If the chngpgs_thresh configuration parameter value is set too low, pages might be written out too early, requiring them to be read back in. If it is set too high, then too many pages may accumulate, requiring users to write out pages synchronously.

When the DB2_USE_ALTERNATE_PAGE_CLEANING registry variable is OFF:

The pool_drty_pg_thrsh_clns monitor element is inserted into the monitor stream.
The pool_drty_pg_thrsh_clns monitor element counts the number of times a page cleaner was invoked because a buffer pool had reached the dirty page threshold criterion for the database.

When the DB2_USE_ALTERNATE_PAGE_CLEANING registry variable is ON:

The pool_drty_pg_thrsh_clns monitor element inserts 0 into the monitor stream.
Page cleaners are always active, attempting to ensure there are sufficient free buffers for victims available instead of waiting to be triggered by the criterion value.