DB2 Version 9.7 for Linux, UNIX, and Windows

select_time - Query Response Time monitor element

This element contains the aggregate amount of time, in milliseconds, that it has taken this data source to respond to queries from all applications or a single application running on this federated server instance since the start of the federated server instance or the last reset of the database monitor counters, whichever is latest.

Note: Due to query blocking, not all attempts by the federated server to retrieve a row result in communication processing; the request to get the next row can potentially be satisfied from a block of returned rows. As a result, the aggregate query response time does not always indicate processing at the data source, but it usually indicates processing at either the data source or client.

Table 1. Snapshot Monitoring Information
Snapshot Level	Logical Data Grouping	Monitor Switch
Database	dbase_remote	Timestamp
Application	appl_remote	Timestamp

For snapshot monitoring, this counter can be reset.

Usage

Use this element to determine how much actual time is spent waiting for data from this data source. This can be useful in capacity planning and tuning the CPU speed and communication rates in SYSCAT.SERVERS. Modifying these parameters can impact whether the optimizer does or does not send requests to the data source.

The response time is measured as the difference in time between the time the federated server requests a row from the data source, and the time the row is available for the federated server to use.