9.6 MyISAM Table Maintenance and Crash Recovery

9.6.1 Using myisamchk for Crash Recovery

9.6.2 How to Check MyISAM Tables for Errors

9.6.3 How to Repair MyISAM Tables

9.6.4 MyISAM Table Optimization

9.6.5 Setting Up a MyISAM Table Maintenance Schedule

This section discusses how to use myisamchk to check or repair MyISAM tables (tables that have .MYD and .MYI files for storing data and indexes). For general myisamchk background, see Section 6.6.4, “myisamchk — MyISAM Table-Maintenance Utility”. Other table-repair information can be found at Section 3.14, “Rebuilding or Repairing Tables or Indexes”.

You can use myisamchk to check, repair, or optimize database tables. The following sections describe how to perform these operations and how to set up a table maintenance schedule. For information about using myisamchk to get information about your tables, see Section 6.6.4.5, “Obtaining Table Information with myisamchk”.

Even though table repair with myisamchk is quite secure, it is always a good idea to make a backup before doing a repair or any maintenance operation that could make a lot of changes to a table.

myisamchk operations that affect indexes can cause MyISAM FULLTEXT indexes to be rebuilt with full-text parameters that are incompatible with the values used by the MySQL server. To avoid this problem, follow the guidelines in Section 6.6.4.1, “myisamchk General Options”.

MyISAM table maintenance can also be done using the SQL statements that perform operations similar to what myisamchk can do:

• To check MyISAM tables, use CHECK TABLE.

• To repair MyISAM tables, use REPAIR TABLE.

• To optimize MyISAM tables, use OPTIMIZE TABLE.

• To analyze MyISAM tables, use ANALYZE TABLE.

For additional information about these statements, see Section 15.7.3, “Table Maintenance Statements”.

These statements can be used directly or by means of the mysqlcheck client program. One advantage of these statements over myisamchk is that the server does all the work. With myisamchk, you must make sure that the server does not use the tables at the same time so that there is no unwanted interaction between myisamchk and the server.