DB2 Version 9.7 for Linux, UNIX, and Windows

rows_read - Rows read monitor element

The number of rows read from the table.

Table 1. Table Function Monitoring Information
Table Function	Monitor Element Collection Level
MON_GET_CONNECTION table function - Get connection metrics	REQUEST METRICS BASE
MON_GET_CONNECTION_DETAILS table function - Get detailed connection metrics (reported in DETAILS XML document)	REQUEST METRICS BASE
MON_GET_SERVICE_SUBCLASS table function - Get service subclass metrics	REQUEST METRICS BASE
MON_GET_SERVICE_SUBCLASS_DETAILS table function - Get detailed service subclass metrics (reported in DETAILS XML document)	REQUEST METRICS BASE
MON_GET_TABLE table function - Get table metrics	Always collected
MON_GET_UNIT_OF_WORK table function - Get unit of work metrics	REQUEST METRICS BASE
MON_GET_UNIT_OF_WORK_DETAILS table function - Get detailed unit of work metrics (reported in DETAILS XML document)	REQUEST METRICS BASE
MON_GET_WORKLOAD table function - Get workload metrics	REQUEST METRICS BASE
MON_GET_WORKLOAD_DETAILS table function - Get detailed workload metrics (reported in DETAILS XML document)	REQUEST METRICS BASE
MON_GET_ACTIVITY_DETAILS table function - Get complete activity details (reported in DETAILS XML document)	ACTIVITY METRICS BASE
MON_GET_PKG_CACHE_STMT table function - Get SQL statement activity metrics in the package cache	ACTIVITY METRICS BASE
MON_GET_PKG_CACHE_STMT_DETAILS table function - get detailed metrics for package cache entries	ACTIVITY METRICS BASE

Table 2. Snapshot Monitoring Information
Snapshot Level	Logical Data Grouping	Monitor Switch
Database	dbase	Basic
Table	table	Table
Application	appl	Basic
Application	stmt	Basic
Application	subsection	Statement
Dynamic SQL	dynsql	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
Connection	event_conn	-
Tables	event_table	-
Statements	event_stmt	-
Transactions	event_xact	-
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

This element helps you identify tables with heavy usage for which you may want to create additional indexes. To avoid the maintenance of unnecessary indexes, use the SQL EXPLAIN statement to determine if the package uses an index.

This count is not the number of rows that were returned to the calling application. Rather, it is the number of rows that had to be read in order to return the result set. For example, the following statement returns one row to the application, but many rows are read to determine the average salary:

 
     SELECT AVG(SALARY) FROM USERID.EMPLOYEE

This count includes the value in the overflow_accesses monitor element. Additionally, this count does not include any index accesses. That is, if an access plan uses index access only and the table is not touched to look at the actual row, then the value of the rows_read monitor element is not incremented.