6.39 Table Activity Metrics

Lists the Table Activity metrics and provides a brief description of each.

Table 6.39 Table Activity Metrics

Name	Description
Created Tmp Disk Tables (Delta)	The total number of temporary tables that were converted to disk based tables, due to exceeding either tmp_table_size or max_heap_table_size.
Created Tmp Files (Delta)	How many temporary files mysqld has created.
Created Tmp Tables (Delta)	The total number of temporary tables created.
Opened Table Definitions (Delta)	The number of .frm files that have been cached.
Opened Tables (Delta)	The total number of tables that have been opened.
Open Table Definitions	The number of currently cached .frm files.
Open Tables	The current number of tables held open in the table cache.
Sort Merge Passes (Delta)	The number of merge passes that the sort algorithm has had to do.
Sort Range (Delta)	The number of sorts that were done using ranges.
Sort Rows (Delta)	The number of sorted rows.
Sort Scan (Delta)	The number of sorts that were done by scanning the table.
Table Locks Immediate (Delta)	The number of times that a request for a table lock could be granted immediately.
Table Locks Waited (Delta)	The number of times that a request for a table lock could not be granted immediately and a wait was needed.
Temporary Disk Table (Rate)	If the space required to build a temporary table exceeds either tmp_table_size or max_heap_table_size , MySQL creates a disk-based table in the server's tmpdir directory. Also, tables that have TEXT or BLOB columns are automatically placed on disk. For performance reasons it is ideal to have most temporary tables created in memory, leaving exceedingly large temporary tables to be created on disk.
Table Cache Not Optimal (Rate)	MySQL is multi-threaded, so there may be many clients issuing queries for a given table simultaneously. To minimize the problem with multiple client threads having different states on the same table, the table is opened independently by each concurrent thread. The table cache is used to cache file descriptors for open tables and there is a single cache shared by all clients. Increasing the size of the table cache allows mysqld to keep more tables open simultaneously by reducing the number of file open and close operations that must be done. If the value of Open_tables is approaching the value of table_cache , this may indicate performance problems.
Table Lock Contention (Rate)	Performance can be degraded if the percentage of table operations that have to wait for a lock is high compared to the overall number of locks. This can happen when using a table-level locking storage engine, such as MyISAM, instead of a row-level locking storage engine.