(
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'T'."~1t\
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c
TRANSFERRING
DATA
After
the
data file has been opened
or
printer
output
specified, data can be trans-
ferred using the shared variable. (An example using tape and printer
input/output
is
shown later
in
this chapter.)
Transferring Data
to
Tape
(OUT
or
ADD
Operation)
When data
is
assigned
to
the shared variable, the data
i~
written on tape and a
return code
is
assigned
to
the
shared variable. A 0 0 return code means
the
data
was transferred successfully and a nonzero return code means
the
transfer of
data failed. See
Return Codes
in
this chapter for a description
of
each return code.
For OUT operations
to
an existing data file (writing new data over
the
existing data),
any existing data following the new data
cannot
be
used again.
For ADD operations,
the
new data
is
written
to
the data file starting
at
the
512-byte
boundary following
the
last record
in
the
file. This might cause'some
tape
storage
to
be unused, for example:
Start
of
the
data for
an OUT operation
512-Byte Boundaries
Unused Tape
Storage
End
of
the data for
an OUT operation
L
Start
of
the
data for an
ADD operation
The unused
tape
storage
that
results from an ADD operation
is
unavailable for use.
However, you can make
all
the
unused tape storage available for use (compress the
data),
as
follows:
1. Transfer the data from
the
data file.
2. Perform an OUT operation
to
write
all
the data back
on
tape.
Data File
163
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