dump_compress_on(5)                                     dump_compress_on(5)
                          Tunable Kernel Parameters



 NAME    [Toc]    [Back]
      dump_compress_on - selects whether the system dumps memory pages
      compressed or uncompressed when a kernel panic occurs.

 VALUES    [Toc]    [Back]
    Failsafe
      0

    Default    [Toc]    [Back]
      1 (Allow the kernel to decide whether to dump compressed or not based
      on the system state at the time of the crash.)

    Allowed value    [Toc]    [Back]
      Integer values 0 and 1.

      The setting for dump_compress_on s used as follows:

           0    Dump uncompressed.

           1    Dump with compression for speed if possible.

    Recommended values    [Toc]    [Back]
      1 (Allow the kernel to choose dump mode.)

      The value the kernel usually chooses is 1.

 DESCRIPTION    [Toc]    [Back]
      On large systems, the time required to dump system memory when a
      kernel panic occurs can be excessive or even prohibitive, depending on
      how much physical memory is installed in the system.  Compressed dump
      capability results in smaller and faster dumps that will also take
      lesser time to save over into the filesystem.

      The crashconf command, and its associated configuration file
      /etc/rc.config.d/crashconf, control which mode should be used for
      dumping.

      The default value for this parameter is 1.  The system determines
      whether or not to dump compressed based on the type of crash that
      occurs, in this case.

      Note that certain types of system crash, require an uncompressed crash
      dump.  Also, the system operator may request an uncompressed crash
      dump at the time the dump is taken.  In either of these cases, an
      uncompressed dump will be performed regardless of the mode selected in
      dump_compress_on.

    Who Is Expected to Change This Tunable?
      Only HP Field engineers should change the value of this tunable.





 Hewlett-Packard Company            - 1 -      HP-UX 11i Version 2: Sep 2004






 dump_compress_on(5)                                     dump_compress_on(5)
                          Tunable Kernel Parameters



    Restrictions on Changing    [Toc]    [Back]
      Changes to this tunable take effect immediately.

    When Should the Tunable Be Turned On?
      This tunable should be turned on to dump compressed when there is a
      system crash.

    What Are the Side Effects of Turning the Tunable Off?
      In this case an uncompressed dump is taken always.  On large memory
      machines, an uncompressed dump take typically three times longer than
      a compressed dump.

    When Should the Tunable Be Turned Off?
      The tunable should be turned off if there is a problem with compressed
      dumps.

    What Are the Side Effects of Turning the Tunable On?
      The system decides the dump mode based on the type of crash.

    What Other Tunables Should Be Changed at the Same Time?
      None.

 WARNINGS    [Toc]    [Back]
      All HP-UX kernel tunable parameters are release specific.  This
      parameter may be removed or have its meaning changed in future
      releases of HP-UX.

      Installation of optional kernel software, from HP or other vendors,
      may cause changes to tunable parameter values.  After installation,
      some tunable parameters may no longer be at the default or recommended
      values.  For information about the effects of installation on tunable
      values, consult the documentation for the kernel software being
      installed. For information about optional kernel software that was
      factory installed on your system, see HP-UX Release Notes at
      http://docs.hp.com.

 AUTHOR    [Toc]    [Back]
      dump_compress_on was developed by Hewlett-Packard Company.

 SEE ALSO    [Toc]    [Back]
      crashconf(1M), alwaysdump(5), dontdump(5).


 Hewlett-Packard Company            - 2 -      HP-UX 11i Version 2: Sep 2004