Guardian Procedure Calls Reference Manual

NOTE: CONTROL 2 is valid only for unstructured files or structured files opened for
unstructured access. For XP-based files, using CONTROL 2 to move the EOF will involve
more CPU cycles. Writing the application data to the file and letting the disk process
move the EOF as the data is written to the file, and removing the CONTROL 2 operations
from the application code will improve the performance.
◦ 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.
• Interprocess communication
Nonstandard operation and parameter values
Any value can be specified for the operation and parameter parameters. An
application-defined protocol should be established for interpreting nonstandard parameter
values.
◦
◦ Process not accepting system messages
If the object of the control operation is not accepting process CONTROL messages, the
call to CONTROL completes with a condition code of CCG; a subsequent call to
FILE_GETINFO_ or FILEINFO shows that an error 7 occurred.
◦ Process control
You can obtain the process identifier of the caller to CONTROL in a subsequent call to
FILE_GETRECEIVEINFO_ (or LASTRECEIVE or RECEIVEINFO).
Related Programming Manuals
For programming information about the CONTROL procedure, see the Guardian Programmer's
Guide, the Enscribe Programmer's Guide, and the data communications manuals.
CONTROL Procedure 211