Managing Systems and Workgroups: A Guide for HP-UX System Administrators

Administering a System: Booting and Shutdown
Abnormal System Shutdowns
Chapter 5540
• “Full Dump vs. Selective Dump” on page 540
• “Dump Definitions Built into the Kernel” on page 540
• “Using a Device for Both Paging and as a Dump Device” on page 541
Full Dump vs. Selective Dump You have chosen this section because it is
most important to you to capture the specific instruction or piece of data that
caused your system crash. The only way to guarantee that you have it is to
capture everything. This means selecting to do a full dump of memory.
Be aware, however, that this can be a costly procedure from both a time and a
disk space perspective. From the time perspective, it can take quite a while to
dump the entire contents of memory in a system with very large amounts of
memory. It can take an additional large amount of time to copy that memory
image to the HP-UX file system area during the reboot process.
From the disk space perspective, if you have large amounts of memory (some
HP-UX systems can now have terabytes of memory), you will need an amount of
dump area at least equal to the amount of memory in your system; and,
depending on a number of factors, you will need additional disk space in your
HP-UX file system area equaling the amount of physical memory in your system,
in the worst case.
Dump Definitions Built into the Kernel There are now a number of places
that you can define which devices are to be used as dump devices:
• During kernel configuration
• At boot time (entries defined in the /etc/fstab file)
• At run time (using the /sbin/crashconf command)
Definitions at each of these places add to or replace any previous definitions from
the other sources. However, consider the following situation:
Example 5-34 Example
In the network named MSW, the system called appserver has one gigabyte (1
GB) of physical memory. If you were to define system dump devices with a total of
256 MB of space in the kernel file, and then define an additional 768 MB of disk
space in the /etc/fstab file, you would have enough dump space to hold the
entire memory image (a full dump) by the time the system was fully up and
running.
But, what if the crash occurs before /etc/fstab is processed? Only the amount
of dump space already configured will be available at the time of the crash; in
this example, 256 MB of space.