Availability Guide for Application Design

Availability in the Pathway Transaction-Processing
Environment
Availability Guide for Application Design—525637-004
6-14
How Does RSC/MP Work?
3. The client process initiates a session with the TDP (RscBeginSession()
function).
4. The client process sends a request to the TDP to begin a transaction
(RscBeginTransaction() function).
5. The TDP converts the RSC/MP call in the message into a call to the TMF interface.
A TMF transaction begins and the TDP gets a transaction identifier, a value that
uniquely identifies the transaction that has just begun.
6. The client process issues a request for a server class to perform an I/O operation
(RscWriteRead() function).
7. The TDP converts the request into a Pathsend call for I/O with the requested
server class. The link manager function works with the PATHMON process to
establish and manage the link and the TDP sends the I/O request directly to the
server process. Refer to Availability Through Pathsend on page 6-18 for details.
8. The server processes the request and replies to the TDP.
9. The TDP performs any necessary conversion and returns the reply to the client
process.
10. The client might issue further I/O requests to the same server class or other server
classes, repeating Steps 6, 7, 8, and 9 for each such request.
11. The client requests the end of the transaction (RscEndTransaction() function).
12. The TDP converts this request into a TMF call and starts the two-phase commit
protocol. The TMF transaction is committed when the TMF call normally returns to
the TDP.
13. The TDP notifies the client that the transaction is committed.
14. The client process performs additional transactions (Steps 4 through 13).
Note that transaction control can also be done automatically by combining a
transaction begin, commit, or abort operation with an I/O function.
For details on writing programs using RSC/MP, refer to the RSC/MP Programming
Manual.
When Is Recovery Action Needed?
Either the system or application must take recovery action if any of the following failure
conditions arises; otherwise, the availability of the application is threatened.
•
A critical processor fails.
•
The TDP stops.
•
A communications line goes down.
•
The server process is lost.
•
The client process stops.