Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (C)
Guardian Procedure Calls Reference Manual—522629-013
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CONTROL Procedure
Considerations
•
Nowait and CONTROL
If the CONTROL procedure is used on a file that is opened nowait, it must be
completed with a call to the AWAITIO procedure.
•
Disk files
•
Writing EOF to an unstructured file
Writing EOF to an unstructured disk file sets the EOF pointer to the relative
byte address indicated by the setting of the next-record pointer and writes the
new EOF setting in the file label on disk. Specifically, write:
end-of-file pointer := next-record pointer;
(File pointer action for CONTROL operation 2, write EOF.)
•
File is locked
If a CONTROL operation is attempted for a file locked through a
filenum
other than that specified in the call to CONTROL, the call is rejected with a “file
is locked” error 73.
If any record is locked in a file, a call to CONTROL to write EOF (operation 2)
to that same file will be rejected with a “file is locked” error 73.
•
Magnetic tapes
•
When device is not ready
If a magnetic tape rewind is performed concurrently with application program
execution (that is, rewind operation <> 6), any attempt to perform a read, write,
or control operation to the rewinding tape unit while rewind is taking place
results in an error indication. A subsequent call to FILE_GETINFO_ or
FILEINFO shows that an error 100 occurred.
•
Wait for rewind to complete
If a magnetic tape rewind operation = 6 (wait for completion) is performed as a
nowait operation, the application waits at the call to AWAITIO for the rewind to
complete.