IBM System/360 System Programmer's Guide

12. You may want to position the tape if you have closed an input data
set before all data has been read.
13. Move your CCW into the channel program area of the control
program's work area. (The symbolic name of the first entry in the
channel program area is DXCCW.)
14. Issue an EXCP macro-instruction specifying the address of the
control prograro's lOB. (The sywtolic name of the lOB is DXIOB.)
15. Techniques used to check for correct volume will differ depending
on the label formats used in the installation.
16. Label processing routines will differ ty label format.
17. If a write operation is requirea, this block can be used.
18. Issue an EXCP macro-instruction specifying the address of the
control program's lOB. (The symbolic name of thE lOB is DXIOB.)
19. Set the high-order bit to 1 in the SRTEDMCT field of the UCB.
20. Use the load multiple instruction (LM).
21. Use the FREEMAIN macro-instruction to free the work area obtained
in step 2.
22. Use the XCTL macro-instruction, specifying the appropriate operand.
The following coding sequence ill~strates an exit from your routine
during OPEN or CLOSE operations.
1. MVC
2 LA
XCTL
MODNAME DC
o (a, 6) , MODNArJjE
15,DXCCW12
EPLOC=(6),DCB=O,SF=(E, (15»
C'IGGxxxxx'
1. The name of the module you are transferring tc is ffioved to the first
8 bytes of the table pointed to by register 6 (see Figure 1).
2 DXCCW12 addresses an eight-byte field that way be used for the remote
supervisor parameter list required by the E-form of the XCTL
macro-instruction.
The following coding sequence illustrates an exit from your routine
during end-of-volume operations.
MVC
LA
LA
XCTL
MODNAME DC
DXCCW12+16(8),MODNAME
15,DXCCW12+8
0, DXCCW12+16
EPLOC=(O) ,DCB=O,SF=(E, (15»
C'IGGxxxxx'
---
The IECDSECT macro-instruction, discussed in the appendix to this
chapter, defines the name DXCCW12. The DCB= parameter of the XCTL
macro-instruction must be coded DCB=O in this application.
INSERTING NONSTANDARD LABEL ROUTINES INTO THE CONTROL PROGRAM
Nonstandard label processing routines must be included in the control
program as part of the SVC library (SYS1.SVCLIB), since they are load
modules of type 4 SVC routines. You insert nonstandard label processing
routines into the control program during the system generation process.
Label Processing Routines 53

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English