SNAX/APC Application Programming Manual

Using the Application Program Interface

SNAX/APC Application Programming Manual—138786

1-22

TP Conversation States

When a TP participates in a conversation, a set of states defines when the TP can issue

specific conversational verb requests. The states are defined by LU 6.2. The state of a

particular TP can change due to verbs issued by the local TP, verbs issued by the remote

TP, or errors in the SNA network.

If a local TP enters into conversations with more than one remote TP, the local TP must

manage the states for each conversation independently.

SNAX/APC defines the following conversation states. Note that verbs may be mapped

or basic—this option is indicated by an (MC) prefix:

RESET

In Reset state, a TP can start a conversation using an (MC)ALLOCATE verb

request. A TP enters Reset state after it terminates a conversation with

(MC)DEALLOCATE.

SEND

From Send state, a local TP can send data to the remote partner TP. A TP usually

enters Send state either after successfully issuing an (MC)ALLOCATE verb request,

or when a (MC)RECEIVE-AND-WAIT or (MC)RECEIVE-IMMEDIATE reply

contains SEND or CONFIRM-SEND in the WHAT-RECEIVED field. A TP also

enters Send state after issuing a (MC)SEND-ERROR verb request.

RECEIVE

In Receive state, a local TP can receive data from the remote partner TP. A TP

enters Receive state by issuing the (MC)RECEIVE-AND-WAIT verb request or the

(MC)PREPARE-TO-RECEIVE verb request from Send state. A target TP begins

operation in Receive state.

CONFIRM, CONFIRM-SEND and CONFIRM-DEALLOCATE

In Confirm states, a TP can reply to a confirmation request (with either

(MC)CONFIRMED or (MC)SEND-ERROR). A TP enters a Confirm state when

the remote TP issues a request verb that requires confirmation. The local TP detects

this when the WHAT-RECEIVED indication in a (MC)RECEIVE-AND-WAIT or

(MC)RECEIVE-IMMEDIATE reply contains CONFIRM, CONFIRM-SEND, or

CONFIRM-DEALLOCATE.

DEALLOCATE

In Deallocate state, a TP can locally deallocate the conversation. A local TP in

Receive state enters Deallocate state when a remote TP requests a

(MC)DEALLOCATE. The local TP receives the verb return code DEALLOCATE-

NORMAL, indicating that it is now in Deallocate state. If the remote TP requested

a (MC)DEALLOCATE with a CONFIRM option, the local TP would first enter

Confirm state.

In Appendix C, Conversation-State Matrix

, Table C-1 lists the verbs (mapped and basic)

that TPs can issue in each conversation state.