13.2 Mettre en place un régime de maintenance

It is a good idea to perform table checks on a regular basis rather than waiting for problems to occur. For maintenance purposes, you can use isamchk -s to check tables. The -s option causes isamchk to run in silent mode, printing messages only when errors occur.

It's a good idea to check tables when the server starts up. For example, whenever the machine has done a reboot in the middle of an update, you usually need to check all the tables that could have been affected. (This is an ``expected crashed table''.) You could add a test to safe_mysqld that runs isamchk to check all tables that have been modified during the last 24 hours if there is an old `.pid' (process ID) file left after a reboot. (The `.pid' file is created by mysqld when it starts up and removed when it terminates normally. The presence of a `.pid' file at system startup time indicates that mysqld terminated abnormally.)

An even better test would be to check any table whose last-modified time is more recent than that of the `.pid' file.

You should also check your tables regularly during normal system operation. At TcX, 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/isamchk -s /path/to/datadir/*/*.ISM

This prints out information about crashed tables so we can examine and repair them when needed.

As we haven't had any unexpectedly crashed tables (tables that become corrupted for reasons other than hardware trouble) for a couple of years now (this is really true), once a week is more than enough for us.

We recommend that to start with, you execute isamchk -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.