AIX 5L Problem Determination - IBM Redbooks

5.9.2 Types of crashes
Common problems requiring crash dump analysis include those discussed in the
following sections.
Kernel panic or trap
A kernel panic or trap is usually the cause of a system crash with the LED
sequence 888-102-700-0cx.
In AIX, kernel panics manifest themselves as traps. The panic() routine in the
kernel puts its message into a buffer, writes it to the debug TTY using the kernel
debug program, and calls brkpoint(). If the kernel debugger is loaded, and an
ASCII terminal is connected on a serial port, this will start the debugger;
otherwise, it will cause a dump. If a panic or assert occurs, you must examine the
source code to understand the condition that caused the panic or assert.
Addressing exception of data storage interrupt
An addressing exception of data storage interrupt is accompanied by the LED
sequence 888-102-300-0cx.
The 300 in the LED sequence indicates an addressing exception (a data storage
interrupt or DSI). This is usually caused by a bad address being accessed, or
page fault occurring when interrupts are disabled. When you get this type of
crash, check the VMM return code.
System hang
A dump can be forced when the system locks up (to determine the cause of the
hang).
A system hang is a total system lockup. A dump forced by turning the key to the
Service position and pressing the Reset button can be examined to see what
locks are being held by whom. Refer to 5.2, “Starting a system dump” on
page 68, for more information.
5.9.3 The snap command
The snap command gathers system configuration information and compresses
the information into a TAR file. The file can then be downloaded to disk or tape,
or transmitted to a remote system. The information gathered with the snap
command may be required to identify and resolve system problems.
Chapter 5. System dumps 95