IBM System/360 System Programmer's Guide

CONSTRUCTING A DUMMY WAITR ROUTINE
The multiprogramming with a fixed number of tasks option (MFT) of
operating System/360 requires programs scheduled into any higher
partitions to release the scheduler as soon after initiation as
possible. The mechanism for release is the WAITR macro-instruction
which causes the required scheduler shift to the next lower paitition.
You may desire to run programs not originally designed for the MFT
environment, i.e., not containing the WAITR macro-instruction, in one of
the higher partitions. In this circumstance you must provide a routine
that will cause the required scheduler shift; invoke the program you
desire to execute; and pass parameters to the invoked program. Your
routine is executed as the first portion of any job with which it is
associated.
The balance of this chapter discusses the functions of a dummy WAITR
routine, provides a coding example, and discusses the job control
language statements and programming considerations pertinent to use of a
dummy WAITR routine.
FUNCTIONS OF THE DUMMY WAITR ROUTINE
When coding a dummy WAITR routine, your code must:
1. Issue a WAITR macro-instruction.
2. Dynamically invoke a specified program.
3. Restore the PARM= field
execution of the WAITR
program to be invoked.
of the EXEC statement that initiated
routine, deleting only the name of the
You use the WAITR instruction to initiate the desired scheduler
shift. You dynamically invoke the program to be executed, i.e.,
transfer control via the XCTL macro-instruction, since once the WAITR
macro-instruction is issued, the scheduler is released. Your WAITR
routine identifies the program to be invoked by picking up its system
name from the PARM= field of the EXEC statement that initiated execution
of your WAITR routine.
Your WAITR routine must restore
parameter(s) present (other than the
picked up by the invoked program.
the PARM= field
invoked program's
so
name)
that
may
any
be
The next section, "A Coding Example" illustrates basic implementation
of these functions.
A CODING EXAMPLE
The following source statement sequence illustrates the implementa-
tion of the dummy WAITR routine functions described in the preceding
section. The statements are keyed to explanatory text by the circled
numbers.
122
DUMWAIT CSECT
SAVE
BALR
USING
ST
LA
L
LH
(14,12)
2,0
*,2
13,MYSAVE+4
13, MYSAVE
3,0(1)
5,0(3)
ADDRESS OF PARM AREA TO GR3
PARM AREA COUNT FIELD TO GR5

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English