Input messages accepted by MFS

Only input data from devices that are defined to IMS TM as operating with MFS can be processed by MFS. However, the use of MFS for specific input messages depends on the message content and, in some cases, on the previous output message.

3770, SLU 1, and NTO

For MFS to process data from a 3770, SLU 1, or NTO, these devices must be defined to operate with MFS at IMS TM system definition or with user descriptors if the extended terminal option (ETO) is available.

After the device is defined to operate with MFS, the terminal still operates in unformatted mode (using basic edit, not MFS) until one of the following occurs:

  • //midname is entered and sent to IMS.
  • An output message to the terminal is processed using a message output descriptor (MOD) that names a message input descriptor (MID) to be used to process subsequent input data.

When //midname is received, MFS gets control to edit the data using the named MID. If any data follows //midname (//midname must be followed by a blank when data is also entered), MFS discards the //midname and the blank and formats the data according to the named MID. If no data follows //midname, MFS considers the next line received from the terminal to be the first line of the message.

When an output message is processed by a MOD that names a MID, the MID is used to format the next input from that terminal. This output message can be created by an application program, the IMS TM /FORMAT command, a message switch, or some other IMS TM function.

Once in formatted mode (using MFS, not IMS TM basic edit), the device continues to operate in formatted mode until one of the following occurs:

  • // or //b (// followed by a blank) is received. The terminal returns to unformatted mode and the // (and blank) are discarded. The two slashes are escape characters.
  • //bH and data are received. The terminal is returned to unformatted mode, the // blank is discarded, and the data is formatted by IMS TM basic edit.
  • An output message whose MOD does not name a MID is sent to the terminal.

3270 and SLU 2

All 3270 and SLU 2 devices are automatically defined to operate with MFS.

Restriction: Situations in which 3270 and SLU 2 devices do not operate in formatted mode are:
  • When first powered on
  • After the CLEAR key is pressed
  • When the MOD used to process an output message does not name a MID to use for the next input data received
  • When MFS is bypassed by the application program using the DFS.EDT or DFS.EDTN modname

While in unformatted mode, input is limited to IMS TM commands, terminal test requests for VTAM® , paging requests, and transaction code or message switch data that does not require MFS.

Finance and SLU P workstations

For MFS to process data from a Finance or SLU P workstation, the terminal must be defined to operate with MFS at IMS TM system definition or with user descriptors if ETO is available. Even when so defined, the workstation operates in unformatted mode (using IMS TM basic edit, not MFS) until one of the following occurs:

  • The Finance or SLU P workstation remote application program requests MFS formatting by specifying the name of a MID in the input message header.
  • //midname is entered by a workstation operator and is sent to IMS TM by the remote application program as the first or only part of the input message itself.

    For proper SLU P formatting, include in the input message header a version identification (version ID). The version ID ensures that the correct level of MFS descriptor (Device Input Format, or DIF) is provided in mapping the input message. If this verification is not desired, the version ID can be sent with hexadecimal zeros (X'0000') or it can be omitted from the message header.

When an output message sent to an SLU P or Finance workstation is formatted using a MOD that names a MID, IMS TM sends the name of the MID to the workstation as part of the output message header. Because IMS TM does not have direct control of the terminal devices in these systems, IMS TM cannot guarantee the proper MID is used to process the next input. It is the responsibility of the remote program to save the MID name and to include it in the next input message it sends to IMS TM as the DPN.

Finance and SLU P workstations continue in formatted mode only when the current message has an associated MID or MOD.

Intersystem communication (ISC) subsystems

For data from an ISC subsystem to be processed by MFS, the ISC subsystem must be defined as UNITYPE=LUTYPE6 on the TYPE macro at IMS TM system definition or with ETO user descriptors. Even when so defined, the ISC subsystem operates in unformatted mode (using IMS TM basic edit or ISC edit, not MFS) until the ISC application program requests MFS formatting by specifying the name of a MID in the DPN field of the input message header.

When an output message sent to an ISC subsystem is formatted using a MOD that names a MID, IMS TM sends the name of the MID to the ISC subsystem in the RDPN field of the output message header. Because IMS TM does not have direct control of the ISC subsystem, IMS TM cannot guarantee the proper MID is used to process the next input. It is the responsibility of the ISC application program to save the MID name and to include it in the next input message it sends to IMS.

ISC subsystems continue in formatted mode only when the current message has an associated MID or MOD.

Formatting messages from terminals in preset destination mode

Preset destination mode is used to fix a destination for all messages entered from a terminal. Use the /SET command to enter preset destination mode. When a terminal is in preset mode, all input messages (processed by either MFS or basic edit) are routed to the destination established by the /SET command. You do not have to include the message destination in the input message.

When IMS TM basic edit processes input from a preset terminal, the preset destination name is added to the beginning of the first segment. When MFS processes input from a preset terminal, the preset destination name is not added to the beginning of the first segment; input message format is a result of your message definition and input. MFS provides many methods for reserving space in an input segment or for inserting a transaction code, without requiring you to specify a message destination.

Formatting of messages using Fast Path

If you plan to implement Fast Path, MFS functions like other IMS TM applications, with the restriction that all messages must be single-segment messages.