ATTACH and SCHEDULER parameters with IMS MFS

The following series of figures illustrate the use of the ATTACH and SCHEDULER parameters when using IMS MFS for IMS input and output messages.

Figure 1. Example of message switch from other subsystem terminal to IMS terminal
From Terminal 1 a non-IMS subsystem sends a message to IMS using DPN=P1, RDPN= , PRN= , RPRN= , and data=... On IMS, the MFS process P1 sends data=(T2)... with a message switch to IMS Terminal 2.
Note: The IMS LTERM name for terminal T2 can be supplied as the input primary resource name (PRN), as a data field, or as an MFS-defined literal. RPRN and RDPN, if supplied, can be optionally included in the data presented to the IMS terminal by MFS. The DPN parameter must be supplied in the input ATTACH FM header to invoke MFS.

In the following figure, a transaction message originates from Terminal 1 and is sent to Process P1 on a non-IMS subsystem. The ATTACH parameters are then used to send the message to the MFS process P2 on the IMS subsystem. The MFS process P2 sends the message to Tran2 in the MPP region. The reply from the MPP region is sent back to the MFS process, which uses the ATTACH parameters to send the reply to the other subsystem. The other subsystem allocates Terminal 1 as a resource of Transaction Tran1 and the message is sent back to the terminal.

Figure 2. Example of other subsystem terminal accesses IMS application program with reply
The non-IMS subsystem uses ATTACH parameters DPN=P2, RDPN=Tran1, PRN= , RPRN=T1, data=... The IMS MFS process uses DPN=Tran1, RDPN=P2, PRN=T1, RPRN= , data=...
Note: The IMS transaction code can be supplied as the input PRN, as a data field (first field for basic edit), or as an MFS-defined literal. The DPN parameter must be supplied to invoke IMS MFS DPM. If a reply inserted by the MPP is processed by MFS, the DPM process might create or override any of the output ATTACH parameters. The input RDPN and RPRN parameters become the output DPN and PRN parameters respectively for any resulting reply from the application program if they are not overridden by the DPM process.

In the following figure, a transaction message originates from Terminal 1 and is sent to Process P1 on a non-IMS subsystem. The ATTACH parameters are then used to send the message to the MFS DPM process P2 on the IMS subsystem. The MFS DPM process P2 sends the message data to Tran2 in the MPP region. The reply from the MPP region is sent back to the MFS DPM process, which uses the ATTACH parameters to send the reply to the non-IMS subsystem as Tran3, which is then stored for later retrieval by Terminal 1.

Figure 3. Example of IMS an MPP accessed from other subsystem terminal with reply to a temporary storage file of the other subsystem
The non-IMS subsystem uses ATTACH parameters DPN=P2, RDPN=Tran3, PRN= , RPRN= , data=... The IMS MFS DPM process uses DPN=Tran3, RDPN=P2, PRN= , RPRN= , data=...
Note: The IMS transaction code can be supplied as the input PRN, as a data field, or as an MFS-defined literal. The DPN parameter must be supplied to invoke IMS MFS DPM. If a reply is inserted by the MPP, the DPM process might override or create any of the output ATTACH parameters. The input RDPN and RPRN parameters become the output DPN and PRN parameters respectively for any resulting reply from the application program if they are not overridden by the DPM process.
Figure 4. Example of a message switch from an IMS terminal to a terminal on another subsystem
Terminal 1 inputs a message to the IMS MFS process on IMS. IMS uses DPN=SCHEDULER, SCDDPN=Tran1, SCDRDPN= , SCDPRN=T2, SCDRPRN=T1, and data=... to send it to terminal T1 on a non-IMS subsystem.

MFS DPM is necessary to create the required output SCHEDULER parameters. The SCDDPN and SCDPRN can be entered as data from the terminal or application program. If a reply is returned to another IMS terminal or application program, the default SCDRPRN parameter can be overridden within the IMS output message's SCHEDULER FM header to specify the suggested IMS terminal or application to receive that reply. The reply is returned with this value in the SCDPRN field.

In the following figure, messages are routed from IMS Terminal 1 to the IMS MFS process either through a message switch or through an MPP or Fast Path message routing application. The MFS process P2 sends the message with SCHEDULER parameters to a transaction on another subsystem. The other subsystem then sends the reply message back using similar SCHEDULER parameters to IMS and the MFS process P2. The MFS edit process directs the message back to Terminal 1.

Figure 5. Example of message routing with IMS MFS
IMS uses DPN=SCHEDULER, SCDDPN=Tran2, SCDRDPN=P2, SCDPRN= , and data=.... to send message. The non-IMS subsystem uses DPN=SCHEDULER, SCDDPN=P2, SCDRDPN= , SCDPRN=T1, SCDRPRN= , and data=... to reply.
Note: The IMS LTERM name can be supplied as the input SCDPRN, as the first data field, or as an MFS-defined literal. The SCDDPN parameter must be supplied to invoke IMS MFS. MFS can override or create any of the output SCHEDULER parameters.