SNAX/HLS Application Programming Manual

SCOBOLX Applications
SNAX/HLS Programming Standards
104707 Tandem Computers Incorporated 1–19
If a WRITEREAD you interrupted completes with 0, its work was already
complete.
If a WRITEREAD you interrupted completes with 187, you have interrupted a
RECEIVE-DATA or RECEIVE-CONTROL-WAIT , and there are no outstanding
activities on the session for which you are responsible.
If a WRITEREAD you interrupted completes with 189, there is still outstanding
work pending on the session whose completion can be obtained by a subsequent
RECEIVE-DATA or similar request.
Users who combine the use of this interrupt facility with pipeline LUs should take
special care. Although the CONTROL 26,0 interrupt request affects only requests you
have issued over the same file, if the request completes with a 189 indicating that the
actual reply is forthcoming, there is no way to predict which accessor of the pipeline
LU will actually retrieve the completion notification. Thus, the use of CONTROL 26,0
on pipeline LUs is strongly discouraged.
OPEN Procedure
The OPEN procedure establishes a connection between your application and
SNAX/HLS. The following restrictions apply to the use of this procedure:
The file name you specify must adhere to the restrictions implied below under
“Connection Types.” In particular, an OPEN that specifies only the process name
of SNAX/HLS is called a server or generic connection, whereas one that in
addition specifies the name of the LU is called a terminal or specific connection.
The sync-depth parameter should be set to a value suitable for the kind of
checkpointing you use. SNAX/HLS retains copies of requests to the depth you
specify. If you specify a value that is too large, there might not be enough storage
allocated SNAX/HLS. Even if checkpointing is not used, you should specify a
sync-depth of 1 to benefit from path recovery.
The nowait I/O depth should be set to 0 if you plan to perform wait I/O.
However, if you plan to use nowait I/O, this value must be set to a value between
1 and 15, depending upon how many simultaneous I/O requests you plan to have
outstanding at one time on this file. If you plan to use the CONTROL 26,0 request,
remember that it counts as one outstanding I/O when issued.
In addition to the responses generated by the file system, SNAX/HLS might generate
any of the following responses:
014 File not found. The format of the OPEN was unacceptable. This usually signifies
that you have used the terminal form, and the name of the LU is improper.
061 No more opens permitted. SNAX/HLS has no room to accept a new opener.