Session Layer - Message Sequence Number Reset

In the event of an application failure, it may be necessary to use the Sequence Reset (tag 35-MsgType=4) message to force synchronization of sequence numbers on the sending and receiving sides. 

In such an event, please be aware of the following:

• Do not use Sequence Reset (tag 35-MsgType=4) as a normal response to a Resend Request (tag 35-MsgType=2) message.

• Use Sequence Reset (tag 35-MsgType=4) message ONLY to recover from a disaster situation that cannot be recovered via the use of Sequence Reset - Gap Fill.

• The Sequence Reset (tag 35-MsgType=4) message is identified as a Reset by setting tag 123-GapFillFlag to 'N' or leaving the tag out of the message.

• If the Sequence Reset (tag 35-MsgType=4) message is sent and is not in response to a Resend Request, tag 43-PossDupFlag should be set to 'N'.

• The Sequence Reset (tag 35-MsgType=4) message must increment the sequence number. A Sequence Reset (tag 35-MsgType=4) with the value in tag 36-NewSeqNo lower than the expected sequence number, logs the client out.

• Tag 36-NewSeqNo of the Sequence Reset (tag 35-MsgType=4) message contains the sequence number of the next message to be transmitted by the sending system. If the message is a Sequence Reset (tag 35-MsgType=4) message and the value in tag 36-NewSeqNo is: Equal to or higher than the expected sequence number, the tag 36-NewSeqNo is adopted as the new expected sequence number of the party that just processed the Sequence Reset (tag 35-MsgType=4) message.

• No acknowledgment is sent in response to the Sequence Reset (tag 35-MsgType=4) message; successful reset will be observed in the next value received in tag 34-MsgSeqNum.