(mysql.info) maintenance-schedule

 
 5.10.4.6 Setting Up a Table Maintenance Schedule
 ................................................
 
 It is a good idea to perform table checks on a regular basis rather
 than waiting for problems to occur. One way to check and repair
 `MyISAM' tables is with the `CHECK TABLE' and `REPAIR TABLE'
 statements. See  check-table, and  repair-table.
 
 Another way to check tables is to use `myisamchk'. For maintenance
 purposes, you can use `myisamchk -s'. The -s option (short for -silent)
 causes `myisamchk' to run in silent mode, printing messages only when
 errors occur.
 
 It is also a good idea to enable automatic `MyISAM' table checking. For
 example, whenever the machine has done a restart in the middle of an
 update, you usually need to check each table that could have been
 affected before it is used further. (These are `expected crashed
 tables.') To check `MyISAM' tables automatically, start the server with
 the -myisam-recover option. See  server-options.
 
 You should also check your tables regularly during normal system
 operation. At MySQL AB, we run a `cron' job to check all our important
 tables once a week, using a line like this in a `crontab' file:
 
      35 0 * * 0 /PATH/TO/MYISAMCHK --fast --silent /PATH/TO/DATADIR/*/*.MYI
 
 This prints out information about crashed tables so that we can examine
 and repair them when needed.
 
 Because we have not had any unexpectedly crashed tables (tables that
 become corrupted for reasons other than hardware trouble) for several
 years, once a week is more than sufficient for us.
 
 We recommend that to start with, you execute `myisamchk -s' each night
 on all tables that have been updated during the last 24 hours, until
 you come to trust MySQL as much as we do.
 
 Normally, MySQL tables need little maintenance. If you are performing
 many updates to `MyISAM' tables with dynamic-sized rows (tables with
 `VARCHAR', `BLOB', or `TEXT' columns) or have tables with many deleted
 rows you may want to defragment/reclaim space from the tables from time
 to time. You can do this by using `OPTIMIZE TABLE' on the tables in
 question.  Alternatively, if you can stop the `mysqld' server for a
 while, change location into the data directory and use this command
 while the server is stopped:
 
      shell> myisamchk -r -s --sort-index --sort_buffer_size=16M */*.MYI
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