Technical data

SDA Description
1 System Management and SDA
The system manager must perform the following operations in regard to the
system dump file:
• Ensure that the system writes a dump file whenever the system fails.
• Ensure that the dump file is large enough to contain all the information to be
saved.
• Ensure that the dump file is saved for analysis.
The following sections describe these tasks.
1.1 Understanding the System Dump File
The operating system attempts to write information into the system dump file
only if the system parameter DUMPBUG is set.
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If DUMPBUG is set and the
operating system fails, the system writes the contents of the error log buffers,
processor registers, and physical memory into the system dump file, overwriting
its previous contents.
If the system dump file is too small, it cannot contain all of memory when a
system failure occurs. For most systems, this means that the system’s page table
(SPT) is not included in the dump. SDA cannot analyze a dump unless the entire
SPT is included in the dump.
1.1.1 Choosing Between SYSDUMP.DMP and PAGEFILE.SYS Files
SYS$SYSTEM:SYSDUMP.DMP (SYS$SPECIFIC:[SYSEXE]SYSDUMP.DMP)
is furnished as an empty file in the software distribution kit. To successfully
store a crash dump, you must make SYS$SYSTEM:SYSDUMP.DMP large
enough to hold all the information to be written when the system fails. If
this is not possible, you can have dumps written into the system paging file,
SYS$SYSTEM:PAGEFILE.SYS. You can enlarge or adjust the size of either of
these files by using the CREATE command of the System Generation utility
(SYSGEN), as described in the OpenVMS System Management Utilities Reference
Manual.
Using SYSDUMP.DMP
To calculate the correct size for SYS$SYSTEM:SYSDUMP.DMP, use the following
formula:
size-in-blocks(SYS$SYSTEM:SYSDUMP.DMP)
= size-in-pages(physical-memory)
+ (number-of-error-log-buffers * blocks-per-buffer)
+1
You can use the DCL command SHOW MEMORY to determine the total size of
physical memory on your system. In addition, you must account for any MA780
multiport memory installed on your system. The number of error log buffers in
any given system varies, depending on the setting of the ERRORLOGBUFFERS
system parameter. (See the OpenVMS System Management Utilities Reference
Manual for additional information about this parameter.)
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The DUMPBUG parameter is set by default. To examine or change its value, consult the
OpenVMS System Management Utilities Reference Manual.
SDA–4