Setting ulimits

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Linux ulimit settings for InfoSphere Streams

The default Linux ulimit settings might be too small for some Red Hat Enterprise Linux (RHEL), Community Enterprise Operating System (CentOS), or SUSE Linux Enterprise Server (SLES) environments, which can cause processing element (PE) failures.

Operating system ulimit settings

When testing InfoSphere® Streams on RHEL, CentOS, and SLES systems, the following ulimit settings were used:

• open files value = 100000
• max user processes value = pending signals value
• pending signals value = 100000

Notes:

• The InfoSphere Streams dependency checker script and checkhost command issue a warning message if the max user processes value is less than or equal to 1024, or the open files value is less than 1024.
• These minimum values might need to be increased based on your InfoSphere Streams applications and environment.

Verifying ulimit settings for InfoSphere Streams

InfoSphere Streams provides the following tools that you can use to verify that the soft ulimit settings for the maximum number of processes and open files are compatible with InfoSphere Streams:

• Before installing the product, use the dependency checker script.
• After installing the product, use the streamtool checkhost command.

If the soft ulimit settings for the maximum number of processes and open files are not compatible with InfoSphere Streams, the following messages are displayed in the command output:

Warning:  CDISI3044W The system limit for the maximum number of processes is low: 1021.
Warning:  CDISI3045W The system limit for the open files is low: 1021.

Reviewing ulimit settings

To review the current ulimit settings on an InfoSphere Streams host, enter the following command:

ulimit -aH

To review the ulimit values that are collected in the runtime boot trace file, enter the following command:

streamtool viewlog --service boot -i instance-id

Updating ulimit settings

Attention: Before changing ulimit settings, contact your system administrator.

There are several ways to change ulimit settings. The following examples show one way to change the settings:

• RHEL and CentOS examples
  • To change the open files value, edit the /etc/security/limits.d/91-nofile.conf file as shown in the following example:

    * - nofile open-files-value

  • To change the max user processes value, edit the /etc/security/limits.d/90-nproc.conf file as shown in the following example:

    * soft nproc max-user-processes-value

• SLES examples
  • To change the open files value, edit the /etc/security/limits.conf file as shown in the following example:

    * - nofile open-files-value

  • To change the max user processes value, edit the /etc/security/limits.conf file as shown in the following example:

    * soft nproc max-user-processes-value

You must restart your system for the changes to take effect.

To verify the updated settings, enter the following command:

ulimit -aH