DB2 Version 9.7 for Linux, UNIX, and Windows

pool_lsn_gap_clns - Buffer pool log space cleaners triggered monitor element

The number of times a page cleaner was invoked because the logging space used had reached a predefined 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

This element can be used to help evaluate whether you have enough space for logging, and whether you need more log files or larger log files.

The page cleaning criterion is determined by the setting for the softmax configuration parameter. Page cleaners are triggered if the oldest page in the buffer pool contains an update described by a log record that is older than the current log position by the criterion value.

When the DB2_USE_ALTERNATE_PAGE_CLEANING registry variable is OFF:

The pool_lsn_gap_clns monitor element is inserted into the monitor stream.
Page cleaners are triggered if the oldest page in the buffer pool contains an update described by a log record that is older than the current log position by the criterion value.

When the DB2_USE_ALTERNATE_PAGE_CLEANING registry variable is ON:

The pool_lsn_gap_clns monitor element inserts 0 into the monitor stream.
Page cleaners write pages proactively instead of waiting to be triggered by the criterion value.