SNAX/APC Application Programming Manual

Using the Application Program Interface
SNAX/APC Application Programming Manual—138786
1-35
Presentation Services (PS) Header Support in Data
Transfer
The GET-TP-PROPERTIES verb returns this LUWID in the UNPROTECTED-LUW-
IDENTIFIER or PROTECTED-LUW-IDENTIFIER field of its reply, depending on the
session allocation sync level.
When SNAX/APC receives an ALLOCATE request from the TP, it validates the
ALLOCATE request for the SYNC-LEVEL parameter. The validation is successful
only if one of the following is true:
•
The SYNCSUPPORT parameter in TP-READY was “Y” and the SYNC-LEVEL
parameter in ALLOCATE is NONE, CONFIRM, or SYNCPT.
•
The SYNCSUPPORT parameter in TP-READY was “N” and the SYNC-LEVEL
parameter in ALLOCATE is NONE or CONFIRM.
Once the ALLOCATE request is validated, a BIND request with the specified sync level
is built and sent to the remote LU. The remote LU replies with a positive response only
if the sync level in the BIND request matches its sync level. Otherwise, a negative
response is sent with sense code X’08350018’, indicating that the requested sync level is
not supported by LU.
On successful session establishment, the local LU builds and sends an ATTACH
(FMH-5) with the requested sync level and the LUWID (protected or unprotected
depending on the SYNC-LEVEL parameter of the ALLOCATE). On receipt of the
ATTACH, the remote LU replies to its pending TP-READY after checking for the sync
level option. The ATTACH with sync level option SYNCPT completes normally only if
there was a pending TP-READY with SYNCSUPPORT “Y”. Otherwise, a negative
response is sent with sense code X’10086041’, indicating that the requested sync level is
not supported by the TP and the session has been deallocated. A sense code
X’10086040’ may also be returned if the BIND request’s sync option does not match the
ATTACH header’s sync option.
Presentation Services (PS) Header Support in Data Transfer
The SYNCPT verb is interpreted by the user-supplied sync point routines using PS
headers. The PS headers are Prepare, Request Commit, Committed, Forget, and
Backout. These are sent to SNAX/APC using SEND-DATA verbs (except Backout,
which is sent using SEND-ERROR).
It is the responsibility of the user-supplied sync point routines to recognize the SYNCPT
verb and correspondingly issue the PS headers to SNAX/APC using SEND-DATA or
SEND-ERROR. SNAX/APC validates and processes the PS headers, transmits them to
the remote side, and changes the direction of the flow accordingly.
Refer to IBM’s LU 6.2 Peer Protocols manual for the PS header format.
When MAPPED conversations are used, the MC-SEND-DATA should have one more
parameter in its request to specify the existence of PS header in the data. This extra
parameter is required in the MC-SEND-DATA because data is not given in the GDS
format used in the SEND-DATA verb.
Figure 1-12
gives the flow of the SYNCPT verb and PS headers during a normal sync
point.