Using KSAM/XL and KSAM 64 (32650-90886)

192 AppendixA
COBOL Intrinsics
CKLOCK
CKLOCK
A call to CKLOCK dynamically locks a KSAM file.
CALL "CKLOCK" USING
filetable, status, lockcond
When access is shared, you must lock the file before calling CKWRITE, CKREWRITE, or
CKDELETE. This ensures that another user cannot attempt to modify the file at the same
time. It guarantees that the most recent data is available to each user who accesses the
file.
In order to call CKLOCK, the file must have been opened with a call to CKOPENSHR, not
CKOPEN.
Parameters
filetable An 8 halfword record containing the number and name of the file, its
input/output type, access mode, and a code indicating whether the
previous operation was successful and if so, what it was. (Refer to Filetable
Parameter discussion earlier in this section.)
status One halfword (two 8-bit characters) set to a pair of values upon completion
of the call to CKLOCK. It indicates whether or not the file was successfully
locked and if not, why not. The
status word = 00 if the call was
successful. It = 30 if the file was locked by another process. It = 9n, where n
is a file system error code, if the call failed for some other reason. (Refer to
the Status Parameter discussion earlier in this section.)
lockcond One halfword computational item whose value determines the action
taken if the file is locked by another user when CKLOCK is executed. The
value is either zero (0) or one (1).
0 locking is conditional; if the file is already locked, control
is returned to your program immediately with the
status
word set to "30".
1 locking is unconditional; if the file cannot be locked
immediately because another use has locked it, your
program suspends until the file can be locked.
Operation Notes
In order to call CKLOCK, the file must be opened with dynamic access enabled. This can be
done only with the CKOPENSHR procedure. CKOPEN will not open the file for shared access
with dynamic locking.
When users are sharing a file, it is essential to lock the file before modifying it. An error is
returned if any user attempts to write, rewrite, or delete records without first locking the
file. It is also important to avoid situations where one user locks the file and forgets to
unlock it. If the file is already locked when you call CKLOCK with
lockcond set to zero, the
call will fail with 30 returned to
status , and your process will continue. If, however,