NET/MASTER Network Control Language (NCL) Reference Manual

MSGREAD
Verbs
106126 Tandem Computers Incorporated 3–135
YES
specifies that NCL is to suspend the MSGPROC process until a message
arrives.
NO
specifies that if no message has arrived, control is to return to the MSGPROC
NCL process immediately, with all specified variables (if any) set to null
values.
nnnn
specifies the number of seconds that the MSGPROC NCL process is to be
suspended for, while waiting for a message to arrive. After this time interval,
control is returned to the MSGPROC NCL process. WAIT=0 (zero) has the
same effect as WAIT=NO.
Considerations
When the MSGREAD verb reads a message it creates an MDO variable beginning
with the stem &$MSG. The MSGREAD verb automatically places the text and the
attributes of the message, such as color and intensity, into the MDO variable. The
MDO variable &$MSG. contains the message profile. It includes attributes such as
color, highlighting, and source information, and provides a complete description
of all the OCS message attributes in addition to the message text. See Section 7,
“Message Profile Variables” for a complete list of these variables.
See EMSREAD, INTREAD, and LOGREAD, which also automatically create MDO
variables mapped by $MSG. For more information on MDO variables, refer to the
NonStop NET/MASTER NCL Programmer's Guide.
The &SYS.FDBK system variable is set on MSGREAD completion. Possible values
of &SYS.FDBK are:
Return
Code
Description
0 Message has been received.
4 Wait time, as defined in the WAIT nnnn operand, has expired.
If a new MDO is created by using the operand MDO=& mdo-name , &SYS.VARCNT
is set to 1.
NCL sets the &SYS.LOOPCTL system variable to 1000 each time the MSGREAD
verb is executed, unless the user explicitly sets it to 0 (zero).
Preloading of a MSGPROC NCL process by using the SYSPARMS PRELOAD
command offers no performance advantage. The procedure remains loaded for
the duration of processing. However, if multiple OCS operators are using the
same MSGPROC NCL process, preloading may offer some storage savings
because only one copy of the process is needed in memory. If not preloaded, one
copy is loaded for each OCS operator requiring the same MSGPROC NCL process.