File descriptors

File descriptors

A file descriptor is a handle created by a process when a file is opened. There is a limit to the amount of file descriptors per process. The default Solaris file descriptor limit is 64.

If the file descriptor limit is exceeded for a process, you may see the following errors:

"Too Many Open Files"
"Err#24 EMFILE" (in truss output)

To display a process' current file descriptor limit, run /usr/proc/bin/pfiles pid | grep rlimit on Solaris systems.

Display system file descriptor settings:
ulimit -Hn (hard limit, cannot be exceeded)
ulimit -Sn / ulimit -n (soft limit may be increased to hard limit value)

Increasing file descriptor settings for child processes (example):
$ ulimit -Hn
1024
$ ulimit -Sn
64
$ ulimit -Sn 1024
$ ulimit -Sn
1024

Solaris kernel parameters:
rlim_fd_cur: soft limit

It may be dangerous to set this value higher than 256 due to limitations with the stdio library. If programs require more file descriptors, they should use setrlimit directly.

rlim_fd_max: hard limit

It may be dangerous to set this value higher than 1024 due to limitations with select. If programs require more file descriptors, they should use setrlimit directly.

More information:
http://www.princeton.edu/~unix/Solaris/troubleshoot/filedesc.html
http://help.netscape.com/kb/corporate/19980403-12.html