HP 3000 Manuals HP 3000 Manuals
Chapter 7 TECHNICAL ARTICLES
SAT Enhancements
by Patrick Murphy
Commercial Systems Division
All System Debug products are capable of reading commands from and
writing command output to a terminal. In addition, both DAT and the
Debugger are capable of reading commands from files with the USE command,
allowing command execution to be fully automated. Likewise, command
output from DAT and the Debugger can be copied to files under the control
of the LIST command. This allows command output to be easily printed or
analyzed by other software.
Because SAT executes in a standalone environment, it does not have a file
system available for the USE and LIST commands to access. For this
reason, USE and LIST have been previously unavailable in SAT, restricting
all command input and output to go through the system console. While it
is still not practical for SAT to access file systems in failed machines,
we have addressed this limitation by creating a new mechanism for SAT to
read commands from and write command output to virtual memory in failed
systems under analysis.
The most convenient way for users or applications to manage virtual
memory for SAT command access is through disk files left opened and
mapped into virtual memory before the system fails. If the mapped
virtual addresses of these files are saved in known locations, such as in
KSOs, then these addresses can be obtained when SAT executes and used in
the new commands described below.
COMMANDS
This section describes how the USE and LIST commands have been adopted
for use by SAT.
USE
SAT commands can be read from virtual memory in the failed machine with
the USE command and its variants.
USE
USEVA virtaddr [count]
USENEXT count
USE CLOSE [ALL|@]
USE, entered alone, displays the current base virtual addresses for
suspended USEVA commands, and the current line position for each.
USEVA begins reading commands from the failed machine starting at virtual
address virtaddr. The commands must be arranged as 80-byte records
positioned contiguously in memory. If a mapped file is used to create
these records, then the blocking factor of the file must be a multiple of
16 to satisfy this requirement. The first blank command record is
treated as end-of-file, and terminates the USEVA command. An optional
count parameter may be used to read a particular number of lines from
virtual memory before returning to interactive user input.
USENEXT count reads the next count lines from the most recently suspended
USEVA command, and then returns to interactive command input.
USE CLOSE terminates the most recently suspended USEVA command.
USE CLOSE ALL or USE CLOSE @ terminates all suspended USEVA commands.
LIST
SAT command input and output can be written to virtual memory in the
failed machine with the LIST command and its variants.
Syntax
LISTVA virtaddr length
LIST ON
LIST OFF
LIST CLOSE
LISTVA begins writing SAT command input and output to virtual memory in
the failed machine starting at virtual address virtaddr. No more than
length bytes are written. All LIST output is arranged in the form of
80-byte records positioned contiguously in memory. If the virtual
address is that of a mapped file, then the blocking factor of the file
should be a multiple of 16 so that the data can be recovered when the
system comes up. The EOF position for the file should also be set at the
file limit.
Note that all list output is written only to the secondary STORE for the
given virtual address. Virtual memory locations present in main memory
are not modified.
CAUTION The LISTVA command must be used cautiously! Since SAT writes
list output to any virtual address, care must be taken not to
inadvertently modify critical system or application data on
disk!
LIST ON and LIST OFF can be used to activate/deactivate the current
LISTVA command. The current position in virtual memory for list output
is retained, but output is not recorded if list output is OFF.
LIST CLOSE terminates the use of the LISTVA virtual address for list
output.
ENVIRONMENTAL VARIABLES
The DATE and TIME environmental variables were previously unimplemented
in SAT, since there was no need to time stamp data that could not be
saved. The new LISTVA command changes this, so these variables are now
available. Please consult the System Debug Reference Manual
(32650-90013) for further details.
SAT COMMAND LINE
Now that SAT is capable of reading commands from virtual memory in the
failed machine, a SATINIT feature has been added, similar to the DATINIT
and DBUGINIT files of DAT and the Debugger.
When SAT is invoked with the SATINIT option at the ISL> prompt or from
the AUTOBOOT file, SAT treats the data in KSO 281 as stored commands in
USEVA format. These commands are executed automatically before SAT
issues a prompt on the console. If either a CONTINUE or EXIT command is
encountered in the KSO, then SAT terminates automatically with no
operator intervention.