HP-UX System Administrator's Guide: Overview HP-UX 11i v3 (B3921-90011, September 2010)

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.
When you define dump devices, whether in a kernel build or at run time, you can list which
classes of memory must always get dumped and which classes of memory should not be dumped.
If you leave both of these lists empty HP-UX will decide for you which parts of memory should
be dumped based on what type of error occurred. In nearly all cases it is best to let HP-UX
determine which pages to dump.
IMPORTANT: You can interrupt the dump at any time by pressing the ESC (escape) key. It can
take as long as 15 seconds to abort.
If you interrupt a dump, it will be as though a dump never occurred; that is, you will not get a
partial dump.
Even if you have defined that you do not want a full dump to be performed, an operator at the
system console at the time of a crash can override those definitions and request a full dump.
80 Major Components of HP-UX