Spotlight on SAP ASE 2.11 - User Guide

Index Read Rate graph

The Index Read Rate graph depicts rates for retrieving index pages from the buffer pools in the database over consecutive monitoring intervals. These rates are based on the number of pages read per second. The graph contains the following series:

• Logical —Plots the rate of index page read requests directed at the buffer pool.

• Physical —Plots the rate at which logical index page requests required actual database I/O to get the index pages into the buffer pool first. When the physical read rate is consistently higher than the logical read rate, the buffer pool is not being used effectively.

• Synch —Plots the rate of synchronous index reads. When synchronous reads are used to retrieve index pages from the database to put them in the buffer pool, further execution of the query is blocked until these reads are complete. A high synchronous read rate can degrade performance.

For related statistical information

The Statistics tab shows the buffer pool write counts used to generate this graph. The names for these statistics begin with either Buffer Pool or I/O. These statistics are derived from the POOL data elements that the DB2 snapshot monitor captures.