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

System-Defined Error Handlers for Specific Conditions
Run-Time Error Handling
106160 Tandem Computers Incorporated 7–25
The following system variables are set specifically for this error handler:
System Variable Setting of System Variable
&SYS.ERROR.VALUE Contains the text of the target label.
&SYS.ERROR.VALUEOK Contains 1 (TRUE) or 0 (FALSE).
See Section 4, “Initial NCL Procedure Development,” for more information on labels.
The LOADFAIL_ERROR
Error Handler
If present, the LOADFAIL_ERROR error handler is raised when NCL cannot find or
load an external NCL procedure or function. This error handler is raised only if the
CONTROL NOFINDRC verb (the default) is set. This error handler is set by the
following ON statement:
ON LOADFAIL_ERROR statement
The following system variables are set specifically for this error handler:
System Variable Setting of System Variable
&SYS.ERROR.VALUE Contains the name of the specified external NCL procedure or function.
&SYS.RETCODE Contains the value of 100 if the CONTROL FINDRC verb is set, otherwise
0.
See Section 8, “Executing NCL Procedures,” for more information on executing an
NCL procedure; and Section 18, “Advanced NCL Programming,” for more
information on the CONTROL verb.
The LOOPING_ERROR
Error Handler
If present, the LOOPING_ERROR error handler traps the case in which the looping
protection mechanism has been triggered: that is, the value of the &SYS.LOOPCTL
system variable has decremented to 0. The CNMREAD, EMSREAD, LOGREAD, and
MSGREAD verbs and the DO, GOSUB, and GOTO core statements decrement
&SYS.LOOPCTL by 1 when executed. This error handler is set by the following ON
statement:
ON LOOPING_ERROR statement
See Section 5, “Controlling Execution Flow,” for more information on the
&SYS.LOOPCTL system variable and the DO, GOSUB, and GOTO core statements;
and Section 17, “Developing System-Level NCL Procedures,” for more on the
EMSREAD, LOGREAD, and MSGREAD verbs.
The PANEL_END Error
Handler
If present, the PANEL_END error handler is invoked as a result of using the PANEL
verb when CONTROL NOPFK is set. It occurs when a user uses the END function key
to remove a panel from display: that is, the user presses the F3 or F16 function key on
a Tandem 6530 or compatible terminal or the PF03 or PF15 function key on an IBM
3270 or compatible terminal.
In a hierarchy of panels, the purpose of the END function key is to allow a user to
move to a panel one level higher in the hierarchy. This error handler is set by the
following ON statement:
ON PANEL_END statement