Exchange/SNA Manual

AWAITIO Procedure
Exchange/SNA System Procedure Calls
104700 Tandem Computers Incorporated 5–3
tag
INT(32):ref:1
returns a unique, application-defined value that your program uses to identify a
particular I/O operation when performing nowait I/O. The value returned is the
value supplied by your program when the nowait I/O operation was initiated.
This parameter is required to identify individual I/O operations when a single file
can have two or more nowait I/O operations outstanding at the same time.
If your program has no more than one outstanding nowait I/O operation against a
single file at one time, you can omit this parameter. In this case, the file number
returned by AWAITIO uniquely identifies the I/O operation that was completed.
time-limit
INT(32):ref:1
specifies whether the call to AWAITIO should check for completion of the I/O
operation and return immediately or wait for completion of the I/O operation.
The allowed values of time-limit are:
> 0D Waits the specified time for completion of the I/O operation. The time to
wait is specified by time-limit in hundredths of a second (.01 seconds).
If the I/O operation does not complete in the specified amount of time,
AWAITIO returns with error number 40. A time-out error completes the
I/O operation (provided you specified a particular file in filenum ), and
the outstanding I/O operation is canceled.
0D Checks for completion of the I/O operation and returns immediately.
If the I/O operation has not yet completed, AWAITIO returns with error
number 40. The outstanding I/O operation is not canceled, and you can
call AWAITIO at a later time to check for completion again.
-1D Waits indefinitely for completion of the I/O operation. There is no limit to
how long your program will wait for the I/O operation to complete.
< -1D Illegal value; the AWAITIO call returns error number 22.
If you set a time limit, make sure that it is long enough to account for poor
response time on the host. Otherwise you may receive false errors (the operation
is running, albeit slowly, but the call times out and returns an error before the
operation can complete).
If you omit the time limit parameter, your program waits indefinitely (no time
limit) for the I/O operation to complete.