State matrix

A conversation enters a particular state when the application program issues an APPCCMD macroinstruction that causes a state transition, or when the application program receives an RCPRI, RCSEC combination or a WHATRCV value that indicates a state transition. The specific state transitions can be found under the heading "State Changes" for each APPCCMD macroinstruction description in the z/OS Communications Server: SNA Programmer's LU 6.2 Reference. State changes as a result of RCPRI, RCSEC return codes can also be found in that manual. (Also see Figure 1 and Figure 2 for half-duplex and full-duplex finite-state machines (FSM) that illustrate the possible conversation state transitions.)

Figure 1. Half-duplex conversation state transitions

Diagram that shows half-duplex finite-state machines (FSM) that illustrate the possible conversation state transitions.

Note:

The initial state of the FSM is reset.
PEND_DEALL is a transient state. The application program can display these states using the APPCCMD CONTROL=TESTSTAT macroinstruction.
The action code specified at each intersection of this FSM matrix can be one of four values.
- A number indicates the next state that the FSM assumes if the matrix intersection is addressed.
- A dash (–) indicates that no state change is to occur.
- A greater-than sign (>) indicates an error condition (and causes a return code indicating STATE_ERROR to be returned to the application program).
- A slash (/) indicates a "cannot-occur" situation, for example, that this matrix intersection cannot be selected because of previous checks that will appear in supporting code.
An "S" in the inputs column indicates that the input is a result of an APPCCMD macroinstruction "sent" by the application program to VTAM®. The inputs associated with an "S" are the values for control and qualify fields on the APPCCMD macroinstruction. An "R" indicates that the input is being "received" by VTAM from the partner LU.

For more information, refer to the individual descriptions of these macroinstructions in the z/OS Communications Server: SNA Programmer's LU 6.2 Reference. Note, however, that the FSM does not attempt to reflect any information concerning the issuance of an APPCCMD macroinstruction in this situation.

Figure 2. Full-duplex conversation state transitions

Diagram that shows full-duplex finite-state machines (FSM) that illustrate the possible conversation state transitions.

Note:

The initial state of the FSM is reset.
The action code specified at each intersection of this FSM matrix can be one of four values.
- A number indicates the next state that the FSM assumes if the matrix intersection is addressed. The state numbers for FSM_CONVERSATION_FDX are shown as hexadecimal values.
- A dash (–) indicates that no state change is to occur.
- A greater-than sign (>) indicates an error condition (and causes a return code indicating STATE_ERROR to be returned to the application program).
- A slash (/) indicates a "cannot-occur" situation, for example, that this matrix intersection cannot be selected because of previous checks that will appear in supporting code.
An "S" in the inputs column indicates that the input is a result of an APPCCMD macroinstruction "sent" by the application program to VTAM. The inputs associated with an "S" are the values for control and qualify fields on the APPCCMD macroinstruction. An "R" indicates that the input is being "received" by VTAM from the partner LU.
The ERROR_INDICATION_RC can be returned to the application on an APPCCMD CONTROL=SEND or an APPCCMD CONTROL=DEALLOC, QUALIFY=FLUSH|DATAFLU macroinstruction. The other inputs received by the application can be returned only on an APPCCMD CONTROL=RECEIVE macroinstruction.