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

Administering a System: Booting and Shutdown
Abnormal System Shutdowns
Chapter 5 539
Compressed Save versus Noncompressed Save System dumps can be very
large, so large that your ability to store them in your HP-UX file system area can
be taxed.
The boot time utility called savecrash can be configured (by editing the file
/etc/rc.config.d/savecrash) to compress or not compress the data as it copies
the memory image from the dump devices to the HP-UX file system area during
the reboot process. This has system recovery time implications in that
compressing the data takes longer. So, if you have the disk space and require
that your system be back up and running as quickly as possible, configure
savecrash to not compress the data.
Using a Device for Both Paging and Dumping It is possible to use a specific
device for both paging (swapping) and as a dump device. If system recovery time
is critical to you, do not configure the primary paging device as a dump device.
From the savecrash (1M) manpage:
By default, when the primary paging device is not used as one of the dump
devices or after the crash image on the primary paging device has been
saved,
savecrash runs in the background. This reduces system boot-up
time by allowing the system to be run with only the primary paging device.
Another advantage to keeping your paging and dump devices separate is that
paging will not overwrite information stored on a dump device, no matter how
long the system has been up or how much activity has taken place. Therefore,
you can prevent savecrash processing at boot time (by editing the file
/etc/rc.config.d/savecrash). This can save you a lot of time when you are
trying to get your system back up in a hurry. After the system is up and running,
you can run savecrash manually to copy the memory image from the dump area
to the HP-UX file system area.
You Can Do a Partial
Save . . .
If a memory dump resides partially on dedicated dump devices and partially on
devices that are also used for paging, you can choose to save (to the HP-UX file
system) only those pages that are endangered by paging activity. Pages residing
on the dedicated dump devices can remain there. If you know how to analyze
memory dumps, it is even possible to analyze them directly from the dedicated
dump devices using a debugger that supports this feature.
Before sending your memory dump to someone else for analysis, you must move
the dumped pages from the dedicated dump devices to the HP-UX file system.
You can then use a utility such as tar to bundle them up for shipment. To move
the dumped pages, use the command /usr/sbin/crashutil to complete the
copy instead of savecrash.
Crash Information Integrity Use this section if the most important
criteria to you is to make sure you capture the part of memory that
contains the instruction or piece of data that caused crash. The factors
you have to consider here are: