NET/MASTER Network Control Language (NCL) Programmer's Guide

Executing Persistent NCL Processes
Environments and Command Processing
16–64 106160 Tandem Computers Incorporated
Executing Persistent
NCL Processes
An NCL process is considered to be persistent when it has automatic restart capability.
Using the RESTART
Operand in the START Verb
When an NCL procedure is started by using the START verb with RESTART=YES or
RESTART=COND, and the START verb also specifies that the NCL process is started
in a background processing environment, a backup process is assigned by NonStop
NET/MASTER MS. The backup process ensures that an NCL process automatically
restarts if a Guardian process or a hardware component fails. An NCL process started
using this method is called a persistent NCL process.
When an NCL process restarts, the NCL ID of the restarted NCL process is unknown.
However, the restarted NCL process does not have the same NCL ID as the original
NCL process.
Number of Restarts in
Persistent NCL
To make an NCL process persistent, the NCL procedure must be started in a
background processing environment using the START verb, and the RESTART
operand must be equal to YES or COND. The value of the &SYS.NCL.RESTART
system variable is initially set to 0 (zero) and increments by 1 each time the NCL
process restarts.
If you try to start the NCL procedure in other than a background processing
environment using the START verb with the RESTART=YES operand, then the
&SYS.RETCODE system variable is set to 48 and the NCL process does not start.
If you try to start the NCL procedure in other than a background processing
environment using the START verb with the RESTART=COND operand, then the
&SYS.RETCODE system variable is set to 52, and the NCL process is not persistent. In
this case, the &SYS.NCL.RESTART system variable has a null value.
Persistent Versus Nonstop
NCL Processes
A persistent NCL process is not a nonstop NCL process. (NonStop NET/MASTER MS
does not support nonstop NCL processes.)
If the CPU in which a persistent NCL process is executing fails for any reason, the
primary processing environment is dismantled and abends. The primary processing
environment is not backed up. Any file or message activity that has occurred during
the execution of the persistent NCL process is not rolled back when the NCL process is
restarted. You can examine the activity log to find any messages generated by the
restarted NCL process.
For further information on persistent NCL, including the syntax of the START verb,
refer to the NonStop NET/MASTER NCL Reference Manual.