Communication Etiquette


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When writing code to be run in transaction mode, you must observe the following rules of basic communication etiquette:

Processes that are participants in the same transaction must require replies for all requests. To include a request that requires no reply, set TPACALL to TPNOTRAN or TPNOREPLY.
A service must retrieve all asynchronous transaction replies before calling TPRETURN or TPFORWAR. This rule must be observed regardless of whether the code is running in transaction mode.
The initiator must retrieve all asynchronous transaction replies (made without TPNOTRAN) before calling TPCOMMIT.
Replies must be retrieved for asynchronous calls that expect replies from non-participants of the transaction, that is, replies to requests made with TPACALL in which the transaction, but not the reply, is suppressed.
If a transaction has not timed out but is marked "abort-only," any further communication should be performed with TPNOTRAN set so that the results of the communication are preserved after the transaction is rolled back.
If a transaction has timed out:
- The handle for the timed-out call becomes stale and any further reference to it returns TPEBADDESC.
- Further calls to TPGETRPLY or TPRECV for any outstanding handles return a global state of transaction timeout; the system sets TP-STATUS to TPETIME.
- Asynchronous calls can be made with TPACALL set to TPNOREPLY, TPNOBLOCK, or TPNOTRAN.
Once a transaction has been marked "abort-only" for reasons other than timeout, a call to TPGETRPLY returns whatever value represents the local state of the call; that is, it returns either success or an error code that reflects the local condition.
Once a handle is used with TPGETRPLY to retrieve a reply, or with TPSEND or TPRECV to report an error condition, it becomes invalid and any further reference to it returns TPEBADDESC. This rule is always observed, regardless of whether the code is running in transaction mode.
Once a transaction is aborted, all outstanding transaction call handles (made without TPNOTRAN) become stale, and any further references to them return TPEBADDESC.