Configuration of MySQLTabLcWaitTest

Table locking enables many sessions to read from a table at the same time, but if a session wants to write to a table, it must first get exclusive access, meaning it might have to wait for other sessions to finish with the table first. During the update, all other sessions that want to access this particular table must wait until the update is done. Table locking causes problems when a session is waiting because the disk is full and free space needs to become available before the session can proceed. In this case, all sessions that want to access the problem table are also put in a waiting state until more disk space is made available. if the number of lock waits grows over time, it will consequently increase the length of the pending requests queue; a long request queue may not only cause the unnecessary erosion of valuable server resources, it may also choke the database server, thereby significantly impacting the quality of the user experience with the server. It is therefore imperative that the lock wait events are monitored, and issues related to such events immediately brought to the attention of administrators.

This test monitors the table lock wait events, and promptly alerts administrators to a sudden/steady increase in the number and duration of such events.

The default parameters associated with this test are:

• The TEST PERIOD list box helps the user to decide how often this test needs to be executed.

• In the HOST text box, specify the HOST for which this test is to be configured.

• In the PORT text box, specify the port at which the target host is listening.

• Specify the name of a database on the target MySQL database server being monitored in the DATABASE textbox.

• The eG agent has to be configured with the credentials of a user who has server-wide Process and Select privileges on the monitored MySQL server. To know how to create such a user, refer to Configuring the eG Agent with Access Privileges topic. Specify the credentials of such a user in the USERNAME and PASSWORD textboxes.

• Confirm the password by retyping it in the CONFIRM PASSWORD textbox.

• By default, the detailed diagnosis of this test, if enabled, will report only the top-10 tables. This is why, the DD ROW COUNT parameter is set to 10 by default. If you want to include more or less tables in detailed diagnosis, then change the value of this parameter accordingly.

• To make diagnosis more efficient and accurate, eG embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test, by default, for a particular server, choose the On option against DETAILED DIAGNOSIS. To disable the capability, click on the Off option.

  The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability.

  • Both the bad and normal frequencies configured for the detailed diagnosis measures should not be 0.

• If multiple components of the same component type are awaiting configuration, then an APPLY TO OTHER COMPONENTS button will appear in this page. Clicking on this button will allow you to apply the configuration to all/selected components of that type.

• Once the necessary values have been provided, clicking on the UPDATE button will register the changes made.

When changing the configuration for specific servers, a “*” beside the text box corresponding to the parameter signifies that these values have to be manually configured by the user. The parameter values that require to be configured will typically be prefixed with a “$” or contain a series of “*”. A value of “none” in the parameter value indicates that the corresponding parameter value can be changed if required.