Orchimate 1.5.0 /

FIX4.2

The sequence reset message is used by the sending application to reset the incoming sequence number on the opposing side. The sequence reset message can be used in the following situations:

• During normal resend processing, the sending application may choose not to send a message (e.g. an aged order). The Sequence Reset can be used to mark the place of that message.
• During normal resend processing, a number of administrative messages are not resent, the Sequence Reset message is used to fill the sequence gap created.
• In the event of an application failure, it may be necessary to force synchronization of sequence numbers on the sending and receiving sides

The sending application will initiate the sequence reset. The message in all situations specifies NewSeqNo to reset as the value of the next sequence number to be transmitted.

If the GapFillFlag field is not present (or set to N), it can be assumed that the purpose of the sequence reset message is to recover from an out-of-sequence condition. The MsgSeqNum in the header should be ignored (i.e. the receipt of a sequence reset message with an out of sequence MsgSeqNum should not generate resend requests).

If the GapFillFlag field is present (and equal to Y), the MsgSeqNum should conform to standard message sequencing rules (i.e. the MsgSeqNum of the SequenceReset-GapFill message should represent the beginning MsgSeqNum in the GapFill range because the remote side is expecting that next message).

The sequence reset can only increase the sequence number. If a sequence reset is received attempting to decrease the next expected sequence number the message should be rejected and treated as a serious error. It is possible to have multiple ResendRequests issued in a row (i.e. 5 to 10 followed by 5 to 11). If sequence number 8, 10, and 11 represent application messages while the 5-7 and 9 represent administrative messages, the series of messages as result of the Resend Request may appear as SeqReset-GapFill with NewSeqNo of 8, message 8, SeqReset-GapFill with NewSeqNo of 10, and message 10. This could then followed by SeqReset-GapFill with NewSeqNo of 8, message 8, SeqReset-GapFill with NewSeqNo of 10, message 10, and message 11. One must be careful to ignore the duplicate SeqReset-GapFill which is attempting to lower the next expected sequence number. This can be detected by checking to see if its MsgSeqNum is less than expected. If so, the SeqReset-GapFill is a duplicate and should be discarded.