The following diagram displays the message flow in the event of an MPUT call to a terminal:
Figure: Message flow for MPUT to terminal
The messages from the program units enter the FORMUSR area via UTM buffers at MPUT time. The size of this area, which must be able to contain the entire logical message, is defined in the NB parameter of the MAX statement (see the openUTM manual “Generating Applications”). This message is formatted by the FHS formatting system MFHSROUT and stored in the FORMIO area. This message is sent to the terminal.
If partial formats are used, you have to make sure that the FORMUSER area is always able to store the entire message.
Input formatting
With input formatting, the message stream runs in the opposite direction, using the same areas.