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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
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