General format of input function management headers (Finance)

IMS transactions, message switches, and commands are in the standard IMS format (transaction code, logical terminal name, or command verb, followed by a blank and text) unless MFS or a Physical Terminal Input edit routine is used to edit the message into the standard format.

The first or only transmission of IMS transactions can have a variable-length FM header. If MFS is not defined for the workstation, the header is ignored. If MFS is defined, the header can contain either an MFS control request or a MID name. For MFS control requests, only the first 2 bytes of the FM header are required.

Byte 0: Header length including the length byte (binary). Bytes 0 and 1 constitute an MFS control request.
Byte 1: Message description (binary).
Byte 2: MID name length (binary).
Bytes 3-10: MID name (1 to 8 bytes) (EBCDIC).

IMS uses the header, but removes it before sending the message to the MPP or MFS. When IMS receives a message with a header, it interrogates the length of the message. If the message length is 2 bytes, IMS assumes that the message is an MFS control request. The MFS control request is indicated in the message description (byte 1).

The PAGEREQ function is not an MFS control request for paging requests.

Related reading: For more information on using the PAGEREQ function, see IMS Version 15.5 Application Programming APIs.