In Health Care Industry,Acknowledgement or Response should be sent back very fast. Once any message received, Acknowledgement should be sent back to TP. Oracle B2B provides a solution to send acknowledgement or Response from transport layer of mllp that is called as immediate acknowledgment.
Immediate acknowledgment is generated and transmitted in the transport layer. It is an alternative to the functional acknowledgment, which generates after processing/validating the data in document layer.

Oracle B2B provides four types of immediate acknowledgment:

Default: Oracle B2B parses the incoming HL7 message and generates an acknowledgment from it. This mode uses the details from incoming payload and generate the acknowledgement based on incoming HL7 message control number, sender and application identification.
By default, an Immediate ACK is a generic ACK. Trigger event can also sent back by using Map Trigger Event property.
If mapping the MSH.10 of the ACK with the MSH.10 of the incoming business message is required, then enable the Map ACK Control ID property.

Simple: B2B sends the predefined acknowledgment message to the sender without parsing the incoming message.

Custom: Custom immediate Ack/Response mode gives a user to define their own response/acknowledgement. This is configurable using file in the Custom Immediate ACK File property.

Negative: In this case, immediate ACK will be returned only in the case of exceptions.