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In MySQL, a temporary table is a special type of table that allows you to store a temporary result set, which you can reuse several times in a single session. In some cases, the server creates internal temporary tables while processing statements. Users have no direct control over when this occurs. If an internal temporary table is created as an in-memory table but becomes too large, MySQL automatically converts it to an on-disk table. The maximum size for in-memory temporary tables is the minimum of the tmp_table_size and max_heap_table_size. If the result set gets bigger than this threshold, MySQL will overflow to-disk based temporary tables. When the size of on-disk temp tables increases beyond threshold, it can cause disk space exhaustion leading to server outages. Because of the continuous outages of the service, the user has to constantly restart the server leading to poor user experience. MySQLTemTabStTest helps administrators in this regard.

This test continuously tracks the total and maximum number of temporary tables created on disk and alerts administrators when the size of the on-disk temporary tables increases beyond the threshold. This way, administrators can be proactively alerted to increasing size of the on-disk temporary tables and thus enabled to rapidly initiate remedial measures to avoid an impending server outage.

Outputs of the test : One set of results for the target MySQL database server being monitored

Measurement	Description	Measurement Unit	Interpretation
TempTabCreatedOnDisk	Indicates the total number of temp tables created on disk during the last measurement period.	Number
MaxTempTabCreatedOnDisk	Indicates the maximum number of internal on-disk temporary tables created by the server while executing statements.	Number	The detailed diagnosis of this measure lists the Thread ID, Statement ID, Schema name, Query duration, Table lock wait time (Seconds), Temp disk tables created, Temp tables created, Rows sent, Rows examined, Select scan, Sort scan and SQL text.