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Spotlight on Oracle 10.9 - Getting Started Guide

Welcome to Spotlight Install Spotlight Start Spotlight Spotlight on Oracle Spotlight on Oracle Data Guard Spotlight on Oracle RAC Spotlight on Unix Spotlight on Windows Spotlight on MySQL Troubleshooting: Connection Problems

Query Cache Page

The MySQL query cache stores the most recent SELECT queries performed by the MySQL database server, together with the result sets of those queries. This can reduce much of the parsing overhead, and logical or physical I/O, associated with those queries if and when the queries are repeated.

The Query Cache page provides details on the activity within the query cache.

To open the Query Cache page

  1. Select the Spotlight on MySQL connection in the Spotlight Browser.
  2. Click Activity | Query Cache.

Query Cache Miss Rate Chart

This chart represents the percentage of SELECT queries issued by clients to the MySQL database server that are NOT found in the query cache. When the miss rate exceeds a specified threshold, Spotlight may raise a Query Cache Hit Rate Alarm.

Query Cache Activity Chart

This chart shows the various types of activity performed within the query cache during the displayed period.

Data Series Description


The rate at which SELECT queries are added to the query cache.


The rate at which queries are removed from the query cache. If this rate grows, you may want to consider increasing the size of the query cache.


The rate at which queries are performed via the query cache. If the hit rate is too low, you may want to consider increasing the size of the query cache.

Not Cached

The rate at which executed SQL statements cannot be cached. This may occur when the statement:

  • Is not a SELECT statement –OR–
  • Is barred from the cache via the SQL_NO_CACHE hint.


The rate at which queries are NOT FOUND in the query cache.

QCache Free Memory

This chart shows the amount of free space available in the query cache for the displayed period. Too little free space may cause cached queries to be removed prematurely from the cache. If so, consider increasing the size of the query cache.

QCache SQL Statements

This chart shows the number of SQL statements stored in the query cache.


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