DB2 Version 9.7 for Linux, UNIX, and Windows

pool_xda_p_reads - Buffer pool XDA data physical reads monitor element

Indicates the number of data pages for XML storage objects (XDAs) read in from the table space containers (physical) for regular and large table spaces.

Table 2. Snapshot Monitoring Information
Snapshot Level Logical Data Grouping Monitor Switch
Database dbase Buffer Pool
Table Space tablespace Buffer Pool
Buffer Pool bufferpool Buffer Pool
Application appl Buffer Pool
Application stmt Buffer Pool
Dynamic SQL dynsql Buffer Pool, Statement
For snapshot monitoring, this counter can be reset.
Table 3. Event Monitoring Information
Event Type Logical Data Grouping Monitor Switch
Activities event_activity (reported in the details_xml document) ACTIVITY METRICS BASE
Activities event_activitymetrics ACTIVITY METRICS BASE
Statistics event_scstats (reported in the metrics document) REQUEST METRICS BASE
Statistics event_wlstats (reported in the metrics document) REQUEST METRICS BASE
Unit of work Reported in the system_metrics document. REQUEST METRICS BASE
Database event_db -
Tablespaces event_tablespace -
Connection event_conn -
Statement event_stmt -
Activities event_activity Buffer Pool, Statement
Package cache Reported in the activity_metrics document. ACTIVITY METRICS BASE
Statistics event_scmetrics* REQUEST METRICS BASE
Statistics event_wlmetrics* REQUEST METRICS BASE
* When returned as part of this logical data group, this element reflects the change in value of this metric since the last statistics collection or database activation, whichever was more recent.

Usage

Use the pool_async_xda_reads and pool_xda_p_reads monitor elements to calculate the number of physical reads that were performed synchronously on XML storage object data pages (that is, physical data page reads that were performed by database manager agents on XML data). Use the following formula:
 
 pool_xda_p_reads + pool_temp_xda_p_reads - pool_async_xda_reads

By comparing the ratio of asynchronous to synchronous reads, you can gain insight into how well the prefetchers are working. This element can be helpful when you are tuning the num_ioservers configuration parameter.

Use the pool_xda_l_reads, pool_xda_p_reads, pool_data_l_reads, and pool_data_p_reads monitor elements to calculate the data page hit ratio for the buffer pool by using the following formula:
 
 1 - ((pool_data_p_reads + pool_xda_p_reads)
    / (pool_data_l_reads + pool_xda_l_reads))