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Tunable Kernel Parameters
HP-UX 11i Version 3: February 2007

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dump_compress_on — selects whether the system dumps memory pages compressed or uncompressed when a kernel panic occur





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

Integer values 0 and 1.

The setting for dump_compress_on is used as follows:


Dump uncompressed.


Dump with compression for speed if possible.

Recommended values

1 (Allow the kernel to choose dump mode.)

The value the kernel usually chooses is 1.


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.

Restrictions on Changing

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?



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.


dump_compress_on was developed by Hewlett-Packard Company.

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