For best product performance, increase the number of file
handles above the default setting of 1024 handles.
About this task
Important: Before you work with
your Rational® product,
increase the number of file handles. Most Rational products use more than the default
limit of 1024 file handles per process. A system administrator might
need to make this change.
Exercise caution when using
the following steps to increase your file descriptors on Linux. If the instructions are not followed
correctly, the computer might not start correctly.
Procedure
To increase your file descriptors:
- Log in as root. If you do not have root access, you must
obtain it before continuing.
- Change to the etc directory.
Attention: If you decide to increase the number of file
handles in the next step, do not leave an empty initscript file on your computer. If you do so, your computer will not start
up the next time that you turn it on or restart.
- Use the vi editor to edit the initscript file in the etc directory. If this file does
not exist, type vi initscript to create it.
- On the first line, type ulimit -n 30000. The point is that 30000 is significantly larger than 1024, the
default value on most Linux computers.
Important: Do not set the number
of handles too high, because doing so can negatively impact system-wide
performance.
- On the second line, type eval exec "$4".
- Save and close the file after making sure that you have
completed steps 4 and 5.
Note: Ensure that you follow
the steps correctly. If this procedure is not completed correctly,
your computer will not start.
- Optional: Restrict the number of handles available
to users or groups by modifying the limits.conf file in the etc/security directory. Both SUSE Linux Enterprise Server (SLES)
Version 9 and Red Hat Enterprise Linux Version 4.0 have this file by default. If you do not
have this file, consider using a smaller number in step 4 in the previous
procedure (for example, 2048). Do this so that most users have a
reasonably low limit on the number of open files that are allowed
per process. If you use a relatively low number in step 4, it is less
important to do this. However, if you set a high number in step 4
earlier and you do not establish limits in the limits.conf file, computer performance can be significantly reduced.
The following sample
limits.conf file restricts
all users, and then sets different limits for others afterwards.
This sample assumes that you set handles to 8192 in step 4 earlier.
* soft nofile 1024
* hard nofile 2048
root soft nofile 4096
root hard nofile 8192
user1 soft nofile 2048
user1 hard nofile 2048
Note that the
* in the preceding example sets the limits for all users first. These
limits are lower than the limits that follow. The root user has a
higher number of allowable handles open, while the number that is
available to user1 is between the two. Make sure that you read and
understand the documentation that the
limits.conf file contains before making changes.
What to do next
For more information on the
ulimit command,
see the man page for
ulimit in the Linux documentation.