Technical data

SDA Description
Using /IGNORE=NOBACKUP
Because system dump files are set to NOBACKUP, the Backup utility
(BACKUP) does not copy dump files to tape unless you use the qualifier
/IGNORE=NOBACKUP when invoking BACKUP. When you use the SDA COPY
command to copy the system dump file to another file, the new file is not set to
NOBACKUP.
As included in the distribution kit, SYS$SYSTEM:SYSDUMP.DMP is protected
against world access. Because a dump file can contain privileged information,
Compaq recommends that you continue to protect dump files from universal read
access.
1.3 Invoking SDA in the Site-Specific Startup Command Procedure
Because a listing of the SDA output is an important source of information
in determining the cause of a system failure, it is a good idea to have SDA
produce such a listing after every failure. The system manager can ensure the
creation of a listing by modifying the site-specific startup command procedure
SYS$MANAGER:SYSTARTUP_VMS.COM so that it invokes SDA when the
system is booted.
When invoked in the site-specific startup procedure, SDA executes the specified
commands only if the system is booting immediately after a system failure. SDA
examines a flag in the dump file’s header that indicates whether it has already
processed the file. If the flag is set, SDA merely exits. If the flag is clear, SDA
executes the specified commands and sets the flag. This flag is clear when the
operating system initially writes a crash dump, except for those resulting from an
operator-requested shutdown (for instance, SYS$SYSTEM:SHUTDOWN.COM).
Using SYSDUMP.DMP
The following example shows typical commands that you might add to your
site-specific startup command procedure to produce an SDA listing after each
failure.
$!
$ ! Print dump listing if system just failed
$!
$ ANALYZE/CRASH_DUMP SYS$SYSTEM:SYSDUMP.DMP
COPY SYS$SYSTEM:SAVEDUMP.DMP ! Save dump file
SET OUTPUT DISK1:SYSDUMP.LIS ! Create listing file
READ/EXEC ! Read symbols into the SDA symbol table
SHOW CRASH ! Display crash information
SHOW STACK ! Show current stack
SHOW SUMMARY ! List all active processes
SHOW PROCESS/PCB/PHD/REG ! Display current process
SHOW SYMBOL/ALL ! Print system symbol table
EXIT
$ PRINT DISK1:SYSDUMP.LIS
The COPY command in the preceding example saves the contents of the file
SYS$SYSTEM:SYSDUMP.DMP. If your system’s startup command file does not
save a copy of the contents of this file, this crash dump information is lost in
the next system failure, when the system saves the information about the new
failure, overwriting the contents of SYS$SYSTEM:SYSDUMP.DMP.
SDA–7