A.2.17 File Not Found

If you get ERROR '...' not found (errno: 23), Can't open file: ... (errno: 24), or any other error with errno 23 or errno 24 from MySQL, it means that you haven't allocated enough file descriptors for MySQL. You can use the perror utility to get a description of what the error number means:

shell> perror 23
File table overflow
shell> perror 24
Too many open files
shell> perror 11
Resource temporarily unavailable

The problem here is that mysqld is trying to keep open too many files simultaneously. You can either tell mysqld not to open so many files at once or increase the number of file descriptors available to mysqld.

To tell mysqld to keep open fewer files at a time, you can make the table cache smaller by using the -O table_cache=32 option to mysqld_safe (the default value is 64). Reducing the value of max_connections will also reduce the number of open files (the default value is 90).

To change the number of file descriptors available to mysqld, you can use the option --open-files-limit=# to mysqld_safe or -O open-files-limit=# to mysqld. See section 4.5.7.4 SHOW VARIABLES. The easiest way to do that is to add the option to your option file. See section 4.1.2 `my.cnf' Option Files. If you have an old mysqld version that doesn't support this, you can edit the mysqld_safe script. There is a commented-out line ulimit -n 256 in the script. You can remove the '#' character to uncomment this line, and change the number 256 to affect the number of file descriptors available to mysqld.

ulimit (and open-files-limit) can increase the number of file descriptors, but only up to the limit imposed by the operating system. There is also a 'hard' limit that can only be overridden if you start mysqld_safe or mysqld as root (just remember that you need to also use the --user=... option in this case). If you need to increase the OS limit on the number of file descriptors available to each process, consult the documentation for your operating system.

Note that if you run the tcsh shell, ulimit will not work! tcsh will also report incorrect values when you ask for the current limits! In this case you should start mysqld_safe with sh!

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