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). The same concepts apply to using isamchk to check or repair ISAM tables (tables that have .ISD and .ISM files for storing data and indexes). For general myisamchk or isamchk background, see Section 4.6.2, “myisamchk — MyISAM Table-Maintenance Utility”.

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 4.6.2.5, “myisamchk Table Information”.

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 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 4.6.2.1, “myisamchk General Options”.

In many cases, you may find it simpler to do MyISAM table maintenance using the SQL statements that perform operations that myisamchk can do:

These statements were introduced in different versions, but all are available from MySQL 3.23.14 on. 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. See Section 12.5.2.1, “ANALYZE TABLE Syntax”, Section 12.5.2.3, “CHECK TABLE Syntax”, Section 12.5.2.5, “OPTIMIZE TABLE Syntax”, and Section 12.5.2.6, “REPAIR TABLE Syntax”.