Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Performance Tuning Guide

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## File Descriptors

You may need to increase the number of file descriptors from the default. Having a higher number of file descriptors ensures that the server can open sockets under high load and not abort requests coming in from clients.

Start by checking system limits for file descriptors with this command:

    cat /proc/sys/fs/file-max
    8192

The current limit shown is 8192. To increase it to 65535, use the following command (as root):

    echo "65535" > /proc/sys/fs/file-max

To make this value to survive a system reboot, add it to `/etc/sysctl.conf` and specify the maximum number of open files permitted:

    fs.file-max = 65535

Note: The parameter is not `proc.sys.fs.file-max`, as one might expect.

To list the available parameters that can be modified using `sysctl`:

    sysctl -a

To load new values from the `sysctl.conf` file:

    sysctl -p /etc/sysctl.conf

To check and modify limits per shell, use the following command:

    limit

The output will look something like this:

    cputime         unlimited
    filesize        unlimited
    datasize        unlimited
    stacksize       8192 kbytes
    coredumpsize    0 kbytes
    memoryuse       unlimited
    descriptors     1024
    memorylocked    unlimited
    maxproc         8146
    openfiles       1024

The `openfiles` and `descriptors` show a limit of 1024. To increase the limit to 65535 for all users, edit `/etc/security/limits.conf` as root, and modify or add the `nofile` setting (number of file) entries:

    *         soft    nofile                     65535
    *         hard    nofile                     65535

The character “`*`” is a wildcard that identifies all users. You could also specify a user ID instead.

Then edit `/etc/pam.d/login` and add the line:

    session required /lib/security/pam_limits.so

On Red Hat, you also need to edit `/etc/pam.d/sshd` and add the following line:

    session required /lib/security/pam_limits.so

On many systems, this procedure will be sufficient. Log in as a regular user and try it before doing the remaining steps. The remaining steps might not be required, depending on how pluggable authentication modules (PAM) and secure shell (SSH) are configured.

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