7.1.3.1 Corrupted MyISAM Tables

Even if the MyISAM table format is very reliable (all changes to a table is written before the SQL statements returns) , you can still get corrupted tables if some of the following things happens:

• The mysqld process being killed in the middle of a write.
• Unexpected shutdown of the computer (for example, if the computer is turned off).
• A hardware error.
• You are using an external program (like myisamchk) on a live table.
• A software bug in the MySQL or MyISAM code.

Typial typical symptoms for a corrupt table is:

• You get the error Incorrect key file for table: '...'. Try to repair it while selecting data from the table.
• Queries doesn't find rows in the table or returns incomplete data.

You can check if a table is ok with the command CHECK TABLE. See section 4.4.4 CHECK TABLE Syntax.

You can repair a corrupted table with REPAIR TABLE. See section 4.4.5 REPAIR TABLE Syntax. You can also repair a table, when mysqld is not running with the myisamchk command. myisamchk syntax.

If your tables get corrupted a lot you should try to find the reason for this! See section A.4.1 What To Do If MySQL Keeps Crashing.

In this case the most important thing to know is if the table got corrupted if the mysqld died (one can easily verify this by checking if there is a recent row restarted mysqld in the mysqld error file). If this isn't the case, then you should try to make a test case of this. See section E.1.6 Making a Test Case If You Experience Table Corruption.

User Comments

Add your own comment.