A tape read ope(ation consists
of
the following IOCBs
and commands:
IOCB
Bytes
Command
0 1 2
Action
Sense
DE
8000
Checks
for
tape
in
place.
Find
DE
8004
Reads
the tape
to
locate header
for
the specified
file.
Read
DE
8001
Reads
the data in a
512-byte
record block.
The tape read operation reads one record
of
data from a
tape. To read successive records from the same file, the
IOCB must
be
updated after each
512-byte
record is
read.
4-14
A tape write operation consists
of
the following IOCBs
and commands:
IOCB
Bytes
Command
0 1 2
Action
Sense
Find
Write
Write
last
Write
header
DE
8000
DE
80
04
DE
8002
DE
80
03
DE
80
DB
Checks
for
tape in
place.
Reads
the tape
to
locate the specified
file.
Writes one
512-byte
record
to
the file.
(This command must be
repeated
for
each
512-byte record written.)
Writes the last data record
and the end
of
data record.
(If the end
of
file is
encountered, only
the
last data record is
written.)
Updates or writes the
new header information.
r"
~_/
/
/
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