Design overview

This section describes the SAA Communications and Resource Recovery interfaces.

The SAA Communications interface

When an application issues an SAA Communications call, control passes via the DFHCPLC application link-edit stub to the common programming interface program (DFHCPI), which in turn passes the request to the DFHCPIC program load module. DFHCPIC verifies the parameters, checks the conversation state, and (if required) issues a DFHLUC macro call to invoke the LU6.2 application request logic module (DFHZARL). For details of DFHZARL, see Distributed transaction processing.

Figure 72 shows how the SAA Communications interface support relates to CICS® intersystem communication (ISC) using VTAM® LU6.2. The numbers in Figure 72 refer to the notes that follow it. CMxxxx represents a program call defined in the SAA Communications interface.

Figure 72. SAA Communications application request processing
 When an application makes an EXEC CICS request using distributed transaction processing (DTP), it is handled by the EXEC interface component (involving DFHEIP, DFHEGL, DFHETC and DFHETL). When an application makes a CMxxxx application request, it is handled by the DFHCPIC load module within the CP component. Both the EXEC interface component and the CP component convert the application's requests into DFHLUC macro requests, that call DFHZARL (for a LU6.2 intersystem link). The SAA Communications interface also uses an RDO object called the PARTNER, encapsulated by the PR component.
Notes:
  1. Distributed transaction processing (DTP) allows a transaction using EXEC CICS commands to communicate with a transaction running in another system. This is carried out by DFHEIP and related EXEC interface processor modules. For a VTAM LU6.2 intersystem link, each request is converted into DFHLUC macro requests that call DFHZARL.
  2. The SAA Communications interface is implemented by the DFHCPIC load module within the CP (or CPI) component. DFHCPIC maps the CMxxxx application requests into DFHLUC macro calls.
  3. To begin a conversation, the SAA Communications interface requires specific information (side information) about the partner program, including its name and system details. This is implemented within CICS as an RDO object called the PARTNER, which is encapsulated by the partner resource manager (PR) component. Further details of the PR component are given under Partner resource manager.

Using the SAA Communications interface on recoverable conversations

When using the SAA Communications interface on recoverable conversations (that is, conversations with the synclevel set to CM_SYNC_POINT), DFHLUC syncpoint requests are routed to DFHZARL via the SAA Communications interface syncpoint request handler (DFHCPSRH) in the DFHCPIC load module. This allows the conversation state to be tracked.

For the equivalent EXEC CICS synclevel 2 conversations, DFHLUC syncpoint requests pass directly to DFHZARL.

The SAA Resource Recovery interface

When an application issues an SAA Resource Recovery call, control passes via the DFHCPLRR application link-edit stub to the common programming interface program (DFHCPI), which in turn passes the request to the DFHCPIRR program load module. DFHCPIRR verifies the parameters, and (if required) issues an appropriate DFHSP macro call: DFHSP TYPE=USER for SRRCMIT, or DFHSP TYPE=ROLLBACK for SRRBACK.

Figure 73 shows how the SAA Resource Recovery interface support relates to the processing of EXEC CICS SYNCPOINT commands. The number in the figure refers to the accompanying note. SRRxxxx represents a program call defined in the SAA Resource Recovery interface, namely, SRRBACK or SRRCMIT.

Figure 73. SAA Resource Recovery application request processing
 EXEC CICS SYNCPOINT commands are handled by the EXEC interface component (DFHEIP and DFHESP), which converts them into DFHSP requests. SRRxxxx application requests are handled by the DFHCPIRR load module in the CP component, which also produces DFHSP requests. DFHSP requests are handled by the recovery manager domain.
Note:
The SAA Resource Recovery interface is implemented by the DFHCPIRR load module within the CP (or CPI) component. DFHCPIRR maps SRRxxxx application requests into DFHSP macro calls.
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