IBM OS/390 User Manual
13.2.6.14 PIOCS
EXCP is often used in VSE in association with card files (for example, SYSIPT),
print files (for example, SYSLST) or the operator console (for example, SYSLOG).
In MVS, EXCP can not be used for spool files or to dialog with the operator. VSE
programs that use EXCP should be converted to use standard access method
such as QSAM or the WTO/WTOR macros.
print files (for example, SYSLST) or the operator console (for example, SYSLOG).
In MVS, EXCP can not be used for spool files or to dialog with the operator. VSE
programs that use EXCP should be converted to use standard access method
such as QSAM or the WTO/WTOR macros.
If IBM-supplied access methods are used in MVS, provide a DCB, issue an OPEN
macro for the data set, and then process it by appropriate I/O macros. It is the
function of the access routines to:
macro for the data set, and then process it by appropriate I/O macros. It is the
function of the access routines to:
•
Provide for CCWs.
•
Construct the IOB (input/output block).
•
Construct the ECB (event control block).
•
Issue an EXCP (execute channel program) macro.
Subsequently, the I/O supervisor schedules the request, issues the START I/O
instruction, handles interrupts, posts results in the form of completion codes,
and, if necessary, executes error recovery routines. Therefore, if the usual
access methods do not apply to a specific problem, you must include in your
program the coding necessary to provide for the preceding access method
functions.
instruction, handles interrupts, posts results in the form of completion codes,
and, if necessary, executes error recovery routines. Therefore, if the usual
access methods do not apply to a specific problem, you must include in your
program the coding necessary to provide for the preceding access method
functions.
Under VSE, only one control block, the CCB, is needed and this control block
may be built by a macro. Under MVS, however, you must allocate and partially
fill the input/output control block and the DECB through the use of DCs.
may be built by a macro. Under MVS, however, you must allocate and partially
fill the input/output control block and the DECB through the use of DCs.
Overview of Programming Elements
In VSE, certain job control statements, system macros, and control blocks are
used. For each of these major programming elements (except SEOV), there is a
corresponding major MVS element. (See Figure 47 on page 320)
used. For each of these major programming elements (except SEOV), there is a
corresponding major MVS element. (See Figure 47 on page 320)
CCB Macro
Figure 53 shows the relationship between the VSE CCB macro operands and
their MVS equivalents:
their MVS equivalents:
Figure 53. Relationship between CCB operands and MVS Equivalents
CCB OPERAND
MVS EQUIVALENT
SYSnnn
DDNAME field of DCB macro. After the OPEN macro has been
executed, the unit control block address for the actual device
is in the DEB.
executed, the unit control block address for the actual device
is in the DEB.
Command-list-name
X
X
′
nnnn
′
(transmission
bytes)
bytes)
CCW address field of IOB. See discussion on CCB Fields.
Sense Address
No corresponding element. The system normally provides the
first two bytes in the IOB.
first two bytes in the IOB.
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