HP-UX System Administrator's Guide: Overview

system back up quickly. And, if you happen to already know why the computer crashed
(for example, if somebody accidently disconnected the wrong cable), there’s little or
no need for a dump anyway.
With HP-UX, a runtime dump subsystem gives you a lot more control over the dump
process. With it you can override dump definitions configured into the kernel while
the system is running. An operator at the system console can even override the runtime
configuration as the system is crashing.
You have control over the following crash dump features:
• Which classes of memory get dumped.
• Run-time crash dump configuration. It is no longer necessary to build your dump
configuration into the kernel file or to reboot the system to change the crash dump
configuration.
• Whether or not a dump is compressed.
These capabilities give you a lot of flexibility, but you need to make some important
decisions regarding how you will configure your system dumps.
There are three main criteria to consider. Select which of these is most important to
you and read the corresponding section. The criteria are:
• System Recovery Time
• Crash Information Integrity
• Disk Space Needs
System Recovery Time
Use this section if your most important criterion is to get your system back up and
running as soon as possible. The factors you have to consider here are:
• Dump Level: Full Dump, Selective Dump, or No Dump
• Concurrent Dumps
• Compressed Save versus Noncompressed Save
• Using a Device for Both Paging and Dumping (System Recovery Time)
• Partial Saves
Dump Level: Full Dump, Selective Dump, or No Dump
In addition to being able to choose “dump everything” or “dump nothing,” you have
the ability to determine which classes of memory pages get dumped, allowing you to
capture important memory structures without having to dump the whole contents of
memory.
You are reading this section because system recovery time is critical to you. Obviously,
the fewer pages your system needs to dump to disk (and on reboot copy to the HP-UX
file system area), the faster your system can be returned to service. Therefore, when
system recovery time is critical avoid using the full dump option.
96 Major Components of HP-UX