IBM System/360 System Programmer's Guide

INPUT - Header labels are verified.
RDBACK - Trailer labels are verified.
OUTPUT - Header labels are created.
If this parameter is omitted, INPUT is assumed.
specifies the volume disposition that is to te provided 'Nhen volume
switching occurs. The operand values and rreanings are as follows:
REREAD
LEAVE
DISP
Reposition the volume to process the data set again.
No additional positioning is performed at end-of-volume
processing.
The disposition indicated on the DD statement is tested
and appropriate positioning provided. This service is
assumed if this operand is omitted and volume position-
ing is applicable. If there is no disposition specified
in the DD statement when this operand is specified,
LEAVE is assurred.
EXCP -- Execute Channel Program
The EXCP macro-instruction requests the initiation of the I/O
operations of a channel program. You must issue EXCP whenever you 'Nant
to execute one of your channel programs. The only parameter of the EXCP
macro-instruction is:
iob-addrx
specifies the address, or a register that contains the address of
the input/output block of the channel program to be executed.
EOV End of Volume
The EOV macro-instruction identifies end-of-volume and end-of-data
set conditions. For an end-of-volume condition, EOV causes s'Nitching of
volumes and verification or creation of standard labels. For an
end-of-data set condition, EOV causes your end-of-data set routine to be
entered. You issue EOV if switching of ~agnetic tape or direct-access
volumes is necessary, or if secondary allocation is to be performed for
a direct-access data set opened for output.
For magnetic tape, you must issue EOV when either a tape mark is read
or a reflective spot is written over. In these cases, bit settings in
the i-byte OFLGS field of the data control block determine the action to
be taken when EOV is executed. Before issuing EOV for magnetic tape,
you must make sure that appropriate bits are set in OFLGS. Bit
positions 2,3,6, and 7 of OFLGS are used only by the system; you are
concerned with bit positions 0,1,4, and 5. The use of these OFLGS bit
positions is as follows:
Bit 0
Bit 1
Bit 4
Bit 5
indicates that a tape mark is to be written.
indicates that a backwards read was the last I/O operation.
indicates that data sets of unlike attributes are to be concatenat-
ed.
indicates that a tape mark has been read.
Execute Channel Program (EXCP) Macro-Instruction 91

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English