If you get
file_name' not found (errno:
Can't open file:
any other error with
file_name (errno: 24)
errno 23 or
errno 24 from MySQL, it means that you have
not 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 OS error code 23: File table overflow shell> perror 24 OS error code 24: Too many open files shell> perror 11 OS 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
system variable (the default value is 64). This may not
entirely prevent running out of file descriptors because in
some circumstances the server may attempt to extend the cache
size temporarily, as described in
Section 18.104.22.168, “How MySQL Opens and Closes Tables”. 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
to mysqld_safe or set the
variable. See Section 5.1.7, “Server System Variables”. The
easiest way to set these values is to add an option to your
option file. See Section 4.2.7, “Using Option Files”. If you have
an old version of mysqld that does not
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.
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
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
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.
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.