ATTACH parameters with the IMS SYSMSG process

The system message process (SYSMSG) is indicated through a special SNA process name in the ATTACH header.

Input system messages for IMS ISC sessions are logged and routed directly to the IMS master terminal operator when no PRN is supplied using the input ATTACH parameters. If a PRN value is supplied for IMS ISC sessions, it becomes the IMS input message destination transaction code or LTERM name (message switch), and the input system message is passed to ISC edit. SYSMSG does not provide access to the IMS command processor.

A reply can result from the input SYSMSG if a PRN value supplied is for an IMS transaction. This reply is sent just as is any other (non-SYSMSG) asynchronous output message.

IMS requests attachment of the SYSMSG process to send IMS broadcast and other system messages that are not directly solicited by an input IMS command.

Exception: When IMS detects an error condition during an input IMS response mode or conversational transaction, an exception response (selective receiver ERP) to the input transaction occurs and the system message is sent as an ERP message.

The following figures illustrate the use of the ATTACH parameters when attaching the SYSMSG process for IMS input and output messages.

Figure 1. Example of SYSMSG without PRN from other subsystem terminal to IMS A
Other subsystem uses DPN=SYSMSG, RDPN= , PRN= , RPRN= , and data=... to send message from Terminal 1 to SYSMSG process in IMS. SYSMSG process sends data=(MTO)... to Master Terminal Operator.
Note: The IMS LTERM name for the master terminal operator is assumed when no input ATTACH PRN parameter is supplied.

In the following figure, the input message from Terminal 1 is routed from a non-IMS subsystem to the IMS SYSMSG process in IMS using ATTACH parameters. The IMS SYSMSG process passes the message to the IMS edit process, which sends the data to tran1 in the IMS MPP region. After tran1 processes, the reply is passed to the IMS edit process again, which uses SCHEDULER parameters to send the reply back to Process 1 and then Terminal 1 on the other subsystem.

Figure 2. Example of SYSMSG with PRN from another subsystem terminal to IMS
Other subsystem uses DPN=SYSMSG, RDPN=P1, PRN=tran1, RPRN=T1, and data=... to send message to IMS. IMS edit process uses DPN=SCHEDULER, SCDDPN=, SCDPRN=T1, SCDRDPN=, SCDRPRN, and data... to send reply.
Note: The PRN parameter becomes the IMS destination. The input RDPN and RPRN parameters become the output DPN and PRN parameters respectively for any resulting reply from the MPP.