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 HP-UX System Administrator's Guide: Overview: HP-UX 11i Version 3 > Chapter 3 Major Components of HP-UX

LiveDump (Memory Dumps of Running Systems)
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Beginning with HP-UX 11i version 3, it is possible to perform dump processing on HP Integrity servers without crashing the system and without causing instability in the system.

Live dumps (memory dumps of systems that have not crashed and are still running) can be useful:

  • For analyzing what caused some recoverable operating system faults

  • In the event of failures with dynamically loadable kernel modules that do not destabilize the kernel (for example, troubleshooting certain problems with I/O drivers)

  • For debugging problems with system performance degradation

  • For analyzing a snapshot of a running kernel off line.

Live dumps can be user initiated or kernel initiated. Users with appropriate privileges can initiate a live dump using the livedump command (see livedump(1M) for details on how to do this).

Limitations of Live Dumps

There are some key differences between live dumps and true crash dumps, some of which represent limitations:

  • The key difference between a live dump versus a crash dump is, of course, that HP-UX continues to run while the dump is in progress.

    The good news is that users of the system continue to work, and are unaffected by the livedump process.

    The bad news is that, because HP-UX continues to run, data structures within the operating system continue to change during the dump process yielding a less accurate picture of the system at the time the dump was initiated. Therefore, the dump saved by livedump can contain some data structures in an inconsistent state. Also, the cause of an event you are troubleshooting might be overwritten (and therefore lost) by ongoing system operations.

  • Do not use livedump on systems that have experienced operating system faults that destabilize the whole system. If a system has become unstable, it is probably better to let it crash on its own or force a crash using a transfer of control (TOC)



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