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 the MySQL server. You can use the
perror utility to get a description of what
the error number means:
shell> perror 23
Error code 23: File table overflow
shell> perror 24
Error code 24: Too many open files
shell> perror 11
Error code 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 reducing the value
of the table_open_cache system variable (the
default value is 64). Reducing the value of
max_connections also reduces the number of
open files (the default value is 100).
To change the number of file descriptors available to
mysqld, you can use the
--open-files-limit option to
mysqld_safe or (as of MySQL 3.23.30) set the
open_files_limit system variable. See
Section 5.2.2, “Server System Variables”. The easiest way to
set these values is to add an option to your option file. See
Section 4.3.2, “Using Option Files”. If you have an old version of
mysqld that doesn't support setting the open
files limit, 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 set the
number of file descriptors to be made available to
mysqld.
--open-files-limit and
ulimit 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 be
overridden only if you start mysqld_safe or
mysqld as root (just
remember that you also need to start the server with the
--user option in this case so that it does not
continue to run as root after it starts up).
If you need to increase the operating system limit on the number
of file descriptors available to each process, consult the
documentation for your system.
Note: If you run the
tcsh shell, ulimit does
not work! tcsh also reports incorrect values
when you ask for the current limits. In this case, you should
start mysqld_safe using
sh.
