Availability Guide for Change Management

Reducing the Time Required for Planned Outages
Availability Guide for Change Management–125506
6-6
Using Parallel Processing
Avoiding Manual Intervention
Write your startup and shutdown files so that they execute correctly without requiring
manual intervention. Any time an operator must intervene, startup and shutdown time is
lengthened. In addition, operator intervention increases the possibility of introducing
unwanted errors that could further delay startup or shutdown.
Using Parallel Processing
Using parallel processing can shorten the time required to start up or shut down your
system or application because startup and shutdown processes are distributed throughout
the processors in your system.
The following examples show how parallel processing can be used to start
communications lines and a transaction-processing application in a PATHMON
environment.
Example 1: Starting Communications Lines
The following command file uses parallel processing in four processors to start several
communications lines. This command file also uses a special technique to handle the
case of a processor that is out-of-service—it attempts to start each SCF process in two
processors. (SCF is a utility that is used to control certain communications subsystems;
the files START0, START1, START2, and START3 contain the actual commands that
start the communications lines.)
If one of the processors is down, the command file continues to the next processor. If
the processor is up, the command file still continues to the next processor but fails
because the process name ($Sn) is now in use by the process that was successfully
started. The result of this technique is that one process is started in the first listed
processor that is up.
SCF /IN START0, NOWAIT, CPU 0, NAME $S0/
SCF /IN START0, NOWAIT, CPU 2, NAME $S0/
SCF /IN START1, NOWAIT, CPU 1, NAME $S1/
SCF /IN START1, NOWAIT, CPU 3, NAME $S1/
SCF /IN START2, NOWAIT, CPU 2, NAME $S2/
SCF /IN START2, NOWAIT, CPU 0, NAME $S2/
SCF /IN START3, NOWAIT, CPU 3, NAME $S3/
SCF /IN START3, NOWAIT, CPU 1, NAME $S3/
When using the technique shown in this command file, make sure that you spread the
process workload across all available processors. If there are too many processes to start
in processors 0 and 1, queueing and memory-contention problems can result. If two
processors are not available, this technique may fail.