Technical data

SDA Description
Note
The ANALYZE/CRASH_DUMP/RELEASE command does not allow you to
analyze the dump before deleting it.
1.1.2 Choosing a Dump File Style
In certain system configurations, it might be impossible to preserve the entire
contents of memory in a disk file. For instance, a large memory system or a
system with small disk capacity might not be able to supply enough disk space
for a full memory dump. In normal circumstances, if the system dump file cannot
accommodate all of memory, SDA cannot analyze the dump.
To preserve those portions of memory that contain information most useful in
determining the causes of system failures, a system manager sets the static
system parameter DUMPSTYLE to 1. When the DUMPSTYLE parameter is
set, AUTOGEN attempts to create a dump file large enough to contain ample
information for SDA to analyze a failure. When the DUMPSTYLE parameter is
clear (the default), AUTOGEN attempts to create a dump file large enough to
contain all of physical memory.
A comparison of full and subset style dump files appears in Table SDA–7.
Table SDA–7 Comparison of Full and Subset Dump Files
Full Subset
Available
Information
Complete contents of physical memory in
use, stored in order of increasing physical
address (for instance, system and global
page tables are stored last).
System page table, global page table,
system space memory, and process and
control regions (plus global pages) for
all saved processes.
Unavailable
Information
Contents of paged-out memory at the time
of the crash.
Contents of paged-out memory at the
time of the crash, process and control
regions of unsaved processes, and
memory not mapped by a page table
(such as the free and modified lists).
SDA Command
Limitations
None. The following commands are not
useful for unsaved processes: SHOW
PROCESS/CHANNELS, SHOW
PROCESS/RMS, SHOW STACK, and
SHOW SUMMARY/IMAGE.
1.2 Saving System Dumps
Every time the operating system writes information to the system dump file, it
writes over whatever was previously stored in the file. For this reason, as system
manager, you need to save the contents of the file after a system failure has
occurred.
Using the SDA COPY Command
You can use the SDA COPY command or the DCL COPY command in your site-
specific startup procedure. Compaq recommends using the SDA COPY command
because it marks the dump file as copied. This is particularly important if the
dump was written into the paging file, SYS$SYSTEM:PAGEFILE.SYS, because
the SDA COPY command releases to the pager the pages that were occupied by
the dump.
SDA–6