IBM OS/390 manual Virtual Storage Macros, Getvis and Freevis Macros

The preceding combination of VSE macro instructions allows you to execute a routine when an operator attention interrupt occurs and to return to the program that was being executed before the interruption.

MVS has no equivalent function. It is possible, however, to simulate this function by using the WTOR macro. This MVS macro writes a message requiring a reply on the operator console and provides the information required by the control program to relay the reply to the issuing program. You must wait for the reply.

This macro could also be executed without a following WAIT macro and coding inserted in the program loop to test the completion of the event. Upon completion, it is possible to execute the communication routine and later resume normal processing. Another solution is to include the communication routine as a subtask with the WTOR macro instruction followed by a WAIT instruction.

Alternately, you can use the Job Control PARM Field (see Register 1 in ªRegister Conventionsº on page 269) to pass information to the program. You may realize throughput improvements because there is no wait for operator′s reply.

Under VSE, you can initiate communication with the background partition using the interrupt key on the console. You can use the MSG (message) command to initiate communication with a foreground partition.

Under MVS, the operator interfaces with job management to provide operator-to-system communication via commands entered on the operator console. This allows the operator to respond to requests from processing programs. However, operator-to-processing program communication must be initiated internally by the processing program. There is no support of the external interrupt key for operator-to-program communication; it switches from the primary to the alternate console.

13.2.4Virtual Storage Macros

13.2.4.1GETVIS and FREEVIS Macros

The MVS GETMAIN, FREEMAIN and STORAGE macros have functions similar to the VSE GETVIS and FREEVIS macros. Example:

(VSE)	GETVIS LENGTH=1000,ADDRESS=PTR1
	LTR	R15,R15	GETVIS OK?
	BNZ	ERROR1	NO, CANCEL
	. . . .
	FREEVIS LENGTH=1000,ADDRESS=PTR1
	. . . .
PTR1	DS	A
(MVS)	GETMAIN RC,LV=1000
	LTR	R15,R15	GETVIS OK?
	BNZ	ERROR1	NO, ABEND
	ST	R1,PTR1	save storage address
	. . . .
	L	R1,PTR1	pick up storage address
	FREEMAIN RC,LV=1000,ADDRESS=(1)
	. . . .
PTR1	DS	A

Chapter 13. A s s e m b l e r 289