ATTIU

The interchange unit code (ATTIU) indicates whether a single input or output IMS message consists of one or more SNA chain.

All input messages that are not MFS-autopaged messages might indicate either single or multiple chain, but are restricted to one actual transmission chain indicating end-of-message. MFS-autopaged input messages might indicate multiple chain regardless of whether the message is actually one or more than one SNA chain. MFS also offers an option that permits single chain messages to produce multiple DPAGEs. Non-MFS and MFS output that is not autopaged is always sent as a single transmission chain with ATTIU indicating single chain. MFS-autopaged output messages are always sent with ATTIU indicating multiple chain.

Restriction: IMS does not support any relationship between consecutive input or output messages. Therefore, the interchange unit code indicating multiple chain cannot be used to send IMS batched input messages or consecutive messages to be scheduled using the SCHEDULER process.

IMS requires attached (synchronous) input message switches to be one chain with at least EB specified.

Restriction: IMS does not support MFS-autopaged synchronous input message switches of more than one SNA chain.

The ATTIU parameter is not automatically retained from one input or output message to another. This parameter must be explicitly provided with each input message, or by MFS if the output message is multichain and is formatted by MFS. The input reset state for ATTIU is multiple chain.