APPC Conversation State Transitions

The following tables show the conversation states in which each APPC verb can be issued, and the state change that occurs on completion of the verb. In some cases, the state change depends on the primary_rc parameter returned to the verb; where this applies, the applicable primary_rc values are listed in the Return codes column.

Where no return codes are shown, the state changes are the same for all return codes (except as described in Notes 2 and 3 following the table).

The possible conversation states are shown as column headings. Against each verb, the following information is given under each heading to indicate the results of issuing the verb in this state:

X indicates that the verb cannot be issued in this state.
The following markers indicate the state of the conversation after the verb has completed:
- Send
- Send Pending
- Receive
- Confirm
- Confirm Send
- Confirm Deallocate
- Pending PoSt
- ReseT
/ indicates that it is not applicable to consider the previous state. This applies to the [MC_]ALLOCATE and RECEIVE_ALLOCATE verbs; these verbs always start a new conversation as though they were in Reset state, with no effect on the conversation (if any) in which they were issued.
A blank entry indicates that the return code shown cannot occur in this state.

For information on full-duplex conversation state transitions, see APPC Full-Duplex Conversation State Transitions.

Table 1. APPC Half-Duplex Conversation State Transitions
Verb Return Codes	T	S	SP	R	C	CS	CD	PS
[MC_]ALLOCATE
AP_OK	S	/	/	/	/	/	/	/
(other)	T
CANCEL_CONVERSATION	X	T	T	T	T	T	T	T
[MC_]CONFIRM	X
AP_OK		S	S	X	X	X	X	X
AP_ERROR		R	R
[MC_]CONFIRMED	X	X	X	X	R	S	T	X
[MC_]DEALLOCATE (Abend)	X	T	T	T	T	T	T	T
[MC_]DEALLOCATE (Other)
AP_ERROR	X	R	R	X	X	X	X	X
(other)		T	T
[MC_]FLUSH	X	S	S	X	X	X	X	X
[MC_]GET_ATTRIBUTES	X	S	SP	R	C	CS	CD	P
GET_STATE	X	S	SP	R	C	CS	CD	P
GET_TYPE	X	S	SP	R	C	CS	CD	P
[MC_]PREPARE_TO_ RECEIVE	X	R	R	X	X	X	X	X
RECEIVE_ALLOCATE	R
AP_OK	T	/	/	/	/	/	/	/
(other)
[MC_]RECEIVE_AND_POST (Note 4)	X	P	P	P	X	X	X	X
[MC_]RECEIVE_AND_WAIT	X	Note 5	Note 5	Note 5	X	X	X	X
[MC_]RECEIVE_IMMEDIATE	X	X	X	Note 5	X	X	X	X
[MC_]REQUEST_TO_SEND	X	X	X	R	C	X	X	P
[MC_]SEND_DATA	X
AP_OK		S	S	X	X	X	X	X
AP_ERROR		R
[MC_]SEND_ERROR	X
AP_OK		S	S	S	S	S	S	S
AP_ERROR		R
[MC_]TEST_RTS	X	S	S	R	C	C	C	P

Note:

In the Return codes column of the table, the abbreviation AP_ERROR is used for the following return codes:
- AP_PROG_ERROR_TRUNC
- AP_PROG_ERROR_NO_TRUNC
- AP_PROG_ERROR_PURGING
- AP_SVC_ERROR_TRUNC
- AP_SVC_ERROR_NO_TRUNC
- AP_SVC_ERROR_PURGING.
The conversation will always enter Reset state if any of the following return codes are received:
- AP_ALLOCATION_ERROR
- AP_COMM_SUBSYSTEM_ABENDED
- AP_COMM_SUBSYSTEM_NOT_LOADED
- AP_CONV_FAILURE_RETRY
- AP_CONV_FAILURE_NO_RETRY
- AP_DEALLOC_ABEND
- AP_DEALLOC_ABEND_PROG
- AP_DEALLOC_ABEND_SVC
- AP_DEALLOC_ABEND_TIMER
- AP_DEALLOC_NORMAL
The following non-OK return codes do not cause any state change. The conversation always remains in the state in which the verb was issued:
- AP_CONVERSATION_TYPE_MIXED
- AP_PARAMETER_CHECK
- AP_STATE_CHECK
- AP_TP_BUSY
- AP_UNEXPECTED_SYSTEM_ERROR
- AP_UNSUCCESSFUL
After [MC_]RECEIVE_AND_POST has been issued and received the initial primary_rc of AP_OK, the conversation changes to Pending Post state. Once the supplied callback routine has been called to indicate that the verb has completed, the new conversation state depends on the primary_rc and what_rcvd parameters as in Note 5.
The state change after one of the RECEIVE verbs depends on both the primary_rc and what_rcvd parameters.
If the primary_rc parameter is AP_PROG_ERROR*, AP_SVC_ERROR*, or ([MC_]RECEIVE_IMMEDIATE only) AP_UNSUCCESSFUL, the new state is RECEIVE.

If the primary_rc parameter is AP_DEALLOC*, the new state is RESET.

If the primary_rc parameter is AP_OK, the new state depends on the value of the what_rcvd parameter:

Receive state

AP_DATA, AP_DATA_COMPLETE, AP_DATA_INCOMPLETE

Send state

AP_SEND

Send Pending state

AP_DATA_SEND, AP_DATA_COMPLETE_SEND

Confirm state

AP_CONFIRM_WHAT_RECEIVED, AP_DATA_CONFIRM, AP_DATA_COMPLETE_CONFIRM

Confirm Send state

AP_CONFIRM_SEND, AP_DATA_CONFIRM_SEND, AP_DATA_COMPLETE_CONFIRM_SEND

Confirm Deallocate state

AP_CONFIRM_DEALLOCATE, AP_DATA_CONFIRM_DEALLOCATE, AP_DATA_COMPLETE_CONFIRM_DEALL

For information on half-duplex conversation state transitions, see APPC Half-Duplex Conversation State Transitions.

Table 2. APPC Full-Duplex Conversation State Transitions
Verb Return Codes	T	SR	S	R
[MC_]ALLOCATE
AP_OK	SR	/	/	/
(other)	T
CANCEL_CONVERSATION	X	T	T	T
[MC_]DEALLOCATE (Abend)	X	T	T	T
[MC_]DEALLOCATE (Flush)	X	R	T	X
[MC_]FLUSH	X	SR	S	X
[MC_]GET_ATTRIBUTES	X	SR	S	R
GET_STATE	X	SR	S	R
GET_TYPE	X	SR	S	R
RECEIVE_ALLOCATE
AP_OK	SR	/	/	/
(other)	T
[MC_]RECEIVE_AND WAIT
AP_OK	X	SR	X	R
AP_ERROR	X	SR	X	R
AP_DEALLOC_NORMAL	X	S	X	T
RECEIVE_EXPEDITED_DATA	X	SR	S	R
[MC_]RECEIVE_ IMMEDIATE
AP_OK	X	SR	X	R
AP_ERROR	X	SR	X	R
AP_DEALLOC_NORMAL	X	S	X	T
[MC_]SEND_DATA
AP_OK	X	SR	S	X
AP_ERROR_INDICATION	X	SR	T	X
[MC_]SEND_ERROR
AP_OK	X	SR	S	X
AP_ERROR_INDICATION	X	SR	T	X

Note:

In the Return codes column of the table, the abbreviation AP_ERROR is used for the following return codes:
- AP_PROG_ERROR_TRUNC
- AP_PROG_ERROR_NO_TRUNC
- AP_SVC_ERROR_TRUNC
- AP_SVC_ERROR_NO_TRUNC
The conversation will always enter Reset state if any of the following return codes are received:
- AP_ALLOCATION_ERROR
- AP_COMM_SUBSYSTEM_ABENDED
- AP_COMM_SUBSYSTEM_NOT_LOADED
- AP_CONV_FAILURE_RETRY
- AP_CONV_FAILURE_NO_RETRY
- AP_DEALLOC_ABEND
- AP_DEALLOC_ABEND_PROG
- AP_DEALLOC_ABEND_SVC
- AP_DEALLOC_ABEND_TIMER
The following non-OK return codes do not cause any state change. The conversation always remains in the state in which the verb was issued:
- AP_CONVERSATION_TYPE_MIXED
- AP_PARAMETER_CHECK
- AP_STATE_CHECK
- AP_TP_BUSY
- AP_UNEXPECTED_SYSTEM_ERROR
- AP_UNSUCCESSFUL

APPC Conversation State Transitions

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