You may in life while working with mysql get the following errors:
ERROR 1016 (HY000) at line 1: Can't open file: './blah/table.frm' (errno: 24)
or
SQL Error (23): Out of resources when opening file
This happens normally because by default the mysql user on most distro’s has a really short limit of 1024 open files, mysql can freak out if you have a large amount of databases or tables.
I triggered this by activating innodb_file_per_table on my setup and having lots of InnoDB tables.
To increase this you need to add the following to /etc/security/limits.conf
mysql soft nofile 10000
mysql hard nofile 20000
and then add the following to the my.inf mysql config (Normally found in /etc/mysql/my.inf)
open_files_limit = 10000
Reboot the mysql server and it should be fixed!
If this is not fixed then please check if the server itself has not ran out of space.