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
Section 12.4.2, “Table Maintenance Statements”.
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 cause the server to check
MyISAM tables automatically, start it with
the --myisam-recover-options
option. See Section 5.1.2, “Server Command Options”.
You should also check your tables regularly during normal system
operation. For example, you can run a cron
job to check 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 you can examine and repair them as necessary.
To start with, execute myisamchk -s each night on all tables that have been updated during the last 24 hours. As you see that problems occur infrequently, you can back off the checking frequency to once a week or so.
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