Message Format Service

Message Format Service (MFS) is an IMS facility that formats messages to and from terminals, so that IMS application programs need not deal with device-specific characteristics in input or output messages.

MFS formats messages to and from user-written programs in remote controllers and subsystems, so that host application programs need not deal with terminal-specific characteristics of the remote controller.

MFS uses control blocks that the user specifies to indicate to IMS how input and output messages are arranged.
  • For input messages, MFS control blocks define how the message that is sent by the device to the application program is arranged in the program's I/O area.
  • For output messages, MFS control blocks define how the message that is sent by the application program to the device is arranged on the screen or at the printer. Data, such as literals that appear on the screen but not in the program's I/O area, can also be defined.

In IMS systems, data that is passed between the application program and terminals or remote programs can be edited by MFS or basic edit. The facilities provided by MFS depend on the type of terminals or secondary logical units (SLUs) your network uses.

MFS allows application programmers to deal with logical messages instead of device-dependent data; this simplifies application development. The same application program can deal with different device types using a single set of logic, whereas device input and output are varied for a specific device type. The presentation of data on the device or operator input can be changed without changing the application program. Full paging capability is provided by IMS for display devices. Input messages are created from multiple screens of data.

A program using MFS need not be designed for the physical characteristics of the device that is used for input and output messages unless it uses very specific device features. Even when these features are used, the program can request that MFS assist in their presentation to the program or the device.

MFS supports SLU-type devices SLU-1, SLU-2, SLU-P, Finance, and LU 6.1. MFS also supports older devices, including IBM® 3270 and 3600.

For IBM 3270 or SLU-2 devices, device control characters or orders can be sent directly from or received by the program using the MFS bypass function. This gives the application program more direct control of the data stream. The program uses reserved format names that cause MFS to bypass the edit of:
  • the output message
  • the next input message that is received from the display terminal

Both logical- and physical-paging facilities are provided for the IBM 3270 and 3604 display stations; these facilities allow the application program to write large quantities of data that MFS can divide into multiple display screens on the terminal. The terminal operator has the capability to page forward and backward to different screens within the message.