Saving the Contents
of the System Dump File After a System Failure
If the system
fails, it overwrites the contents of the system crash dump file
and the previous contents are lost. For this reason, ensure that
your system automatically analyzes and copies the contents of the
system dump file each time the system reboots.
On Alpha and I64 systems, SDA is invoked by default during
startup, and a CLUE list file is created. Generated by a set sequence
of commands, the CLUE list file contains only an overview of the
crash and might not provide enough information to determine the
cause of the crash. HP, therefore, recommends that you always
copy the system dump file.
Refer to the OpenVMS System Analysis Tools Manual
for
information about modifying your site-specific command procedure
to execute additional commands such as SDA COPY upon startup after
a system failure.
On VAX systems, modify
the site-specific startup command procedure SYSTARTUP_VMS.COM so
that it invokes the System Dump Analyzer utility (SDA) when the
system is booted.
Be aware of the following facts:
When invoked from the site-specific
startup procedure in the STARTUP process, SDA executes the specified
commands only if the system is booting immediately after a system
failure. If the system is rebooting after it was shut down with
SHUTDOWN.COM or OPCCRASH.EXE, SDA exits without executing the commands.
Although you can use the DCL command COPY to copy
the dump file, the SDA command COPY is preferable because it copies
only the blocks occupied by the dump and it marks the dump file
as copied. The SDA COPY command is preferable also when the dump
was written into the paging file, SYS$SYSTEM:PAGEFILE.SYS, because
the SDA COPY command releases to the pager those pages occupied
by the dump. For more information, see
Freeing Dump Information from the Page File.
Because a system dump file can contain privileged
information, protect copies of dump files from world read access.
For more information about file protection, refer to the HP OpenVMS Guide to System Security.
System dump files have the NOBACKUP attribute, so
the Backup utility (BACKUP) does not copy them unless you use the
qualifier /IGNORE=NOBACKUP when invoking BACKUP. When you use the
SDA command COPY to copy the system dump file to another file, the
operating system does not automatically set the new file to NOBACKUP.
If you want to set the NOBACKUP attribute on the copy, use the SET FILE
command with the /NOBACKUP qualifier as described in the HP OpenVMS DCL Dictionary.
The SDA command COPY in the following example saves the contents
of the file SYS$SYSTEM:PAGEFILE.SYS and performs some analysis of
the file. Note that the COPY command is the final command because
the blocks of the page file used by the dump are released as soon
as the COPY command completes, and can be used for paging before
any other SDA commands can be executed.
$ !
$ ! Print dump listing if system just failed
$ !
$ ANALYZE/CRASH_DUMP SYS$SYSTEM:PAGEFILE.SYS
SET OUTPUT DISK1:SYSDUMP.LIS ! Create listing file
READ/EXECUTIVE ! Read in symbols for kernel
SHOW CRASH ! Display crash information
SHOW STACK ! Show current stack
SHOW SUMMARY ! List all active processes
SHOW PROCESS/PCB/PHD/REG ! Display current process
COPY SYS$SYSTEM:SAVEDUMP.DMP ! Save system dump file
EXIT
$ SET FILE/NOBACKUP SYS$SYSTEM:SAVEDUMP.DMP