HP-UX 11i Version 1.5 System Crash Dump

Crash Dump Conﬁguration

Chapter 1 15

and how much space a selective dump will take. This information can be

used to determine the amount of dump space that should normally be

conﬁgured. Specifying “-v ” on the crashconf(1M) command line will

display the current crash dump conﬁguration to verify that the expected

changes have taken effect.

How Much Dump Space Do I Need?

For selective dumps, use crashconf(1M) to ﬁnd out how much space

would be needed for a selective dump of your machine. (Use the -v ﬂag,

and run it while your system is under its normal or higher than normal

workload.) The space needed will vary depending on the workload of the

machine, so add another 25% or so to be safe. The total dump space

should meet or exceed this amount.

For machines that are relatively stable and don’t expect to dump often,

this is enough. If a full dump is needed from such a machine, additional

space can be conﬁgured for it on the ﬂy, anyway. This space can also be

used for swap unless reboot times are critical.

For machines on which full dumps are required, the full size of physical

memory, plus a little bit for dump headers and tables, should be

conﬁgured as dump space. At least the amount needed for a selective

dump should be conﬁgured on a device that is not used for swap activity.

For example, the size of a selective dump for a 1GB RAM system

typically ranges from 100MB to 200MB (10% to 20%). Extrapolating this

to a 64GB system, a dump could be as large as 12GB.

Whenever you have dump devices that are not also used for swap

activity, make sure that they are conﬁgured last. This will cause them to

be used ﬁrst (dump goes from the end backward), which will minimize

the chance of writing into an area shared by swap. Writing into swap

space is undesirable because it will slow down your reboot processing;

see “Post-Reboot Dump Processing” on page 17, for details.