SNAX/APN Application Programming Manual

The SNALU Interface
SNAX/APN Application Programming Manual—420111-001
4-18
Normal/Expedited Flows
Normal/Expedited Flows
Within a SNAX/APN environment, an application can use normal or expedited-flow
RUs with the remote LU and normal-flow RUs with the SNAX/APN logon manager
(TLOGMGR):
•
LU-LU normal flow
Because sequence numbers are required for LU-LU sessions, both LUs involved in
the session attach sequence numbers to all outgoing normal-flow LU-LU requests
and responses. The two sets of sequence numbers (those generated by the PLU and
those generated by the SLU) are independent of each other.
Each LU assigns the sequence number X'0001' to the first outgoing normal-flow
LU-LU BIU and increments the sequence number by one for each successive
outgoing normal-flow LU-LU BIU. This practice continues until either the session
is terminated or until the PLU sends an STSN (Set and Test Sequence Numbers)
request to the SLU.
•
LU-TLOGMGR normal flow
When formatting a response, the PLU or SLU uses the sequence number of the
request that is being responded to. Should an exception response or write error 182
occur, the PLU or SLU can often use the sequence number to determine where the
error occurred. Sequence numbers are also useful for logical units that log each
request sent or received.
When communicating with one another, both the PLU or SLU and the SNAX/APN
logon manager (TLOGMGR) attach identifiers to all outgoing requests and
responses. The two sets of identifiers (those generated by the PLU or SLU and
those generated by the TLOGMGR) are independent of one another.
The identifier is usually used in a manner similar to the sequence numbers of
normal-flow LU-LU requests and responses. However, there are no rules regarding
its usage (for example, the identifiers do not have to begin at X'0001' or be
incremented sequentially).
When formatting a response, the PLU or SLU and the TLOGMGR use the sequence
identifier of the request to which it is responding.
•
LU-LU Expedited-Flow
Within a SNAX/APN environment, an application only uses the expedited flow for
communicating with the remote LU. All communication with the SNAX/APN
logon manager (TLOGMGR) is handled by way of normal flow.
Both LUs involved in the session attach identifiers to all outgoing expedited flow
LU-LU requests and responses. This identifier is similar to the identifiers used in
normal-flow RUs between an LU and a TLOGMGR. There are no rules regarding
its usage (for example, the identifiers do not have to begin at X'0001' or be
incremented sequentially).
When formatting a response, the PLU or SLU uses the identifier of the request to
which it is responding.