IBM RS/6000 - Manual (Page 104)

Change the Directory to which Dump is Copied on Boot
choosing a filesystem which will have enough space, determined by step 1, to
accommodate the dump on reboot. Enter the following command (for example,
using the /var filesystem):
sysdumpdev -d /var
In the above example, if the system were to crash and save a system dump in the
paging space, upon reboot, AIX would copy the dump into the /var filesystem.
5.3.2 Creating a Logical Volume for the System Dump
If you have spare disk space, you may wish to set up a dedicated logical volume to
store the dump if one occurs (this was the default with AIX V3.2). To do this,
perform the following steps:
1. Determine how much space will be required by the dump. Enter the following
command:
sysdumpdev -e
2. Use the following SMIT fastpath:
smit lv
Add a Logical Volume
And create a logical volume of at least the size determined by step 1.
Alternatively, you can use the following from the command line (for example,
creating /dev/hd7 as your dump logical volume):
mklv -t sysdump -y hd7 rootvg pp
where pp is the number of 4 megabyte partitions required.
3. Set the primary dump device to /dev/hd7 using SMIT:
smit dump
Change the Primary Dump Device
or use the following command:
sysdumpdev -P -p'/dev/hd7'
In the above example, the system, if the machine crashed, would store the dump in
/dev/hd7, and the dump would be available on reboot. The dump will remain in
/dev/hd7 until another system crash occurs.
5.3.3 Initiating a System Dump
With microchannel-based RS/6000 systems, a system dump can be initiated by the
root user using any of the following three methods:
1. Setting the physical key to Service and pressing the reset button.
2. Pressing CTL-ALT-NUNPAD1 or CTL-ALT-NUMPAD2 on the keyboard of a
graphical console.
3. Using SMIT to start a dump:
smit dump
Start a Dump to the Primary Dump Device
80 Introduction to PCI-Based RS/6000 Servers