SeqReset-Gap Fill messages vs SeqReset-Reset message

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Imported from previous forum

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[ original email was from Rajan Rajput - ]
I understand that SeqReset-GapFill message is sent only in response to a resend request unlike a SeqReset-Reset message. However, from the 4.0 specs it seems that SeqReset-Reset message can always be used instead of SeqReset-GapFill message. Can you please give examples of any cases where it is preferrable to send SeqReset-GapFill message, and why.

Thanx.
Rajan.

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[ original email was from Scott Atwell - ]
It is possible to use either, but there are definitely cases in which the Gap Fill is preferable, though. Basically if you a resend request will result in a contiguous series of MsgSeqNum’s which should not be resent, a single SequenceReset with the Gap Fill flag can be sent (and a single message processed by the counterparty) vs. one Sequence Reset for each message.

In FIX 4.0, all messages consume sequence numbers including
Heartbeat, Test Request, Logon, Logout, etc. A SequenceReset with Gap Fill could be used to skip over 100
Heartbeats, for instance.

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[ original email was from Charles Easton - upchuk@optonline.net ]
> I understand that SeqReset-GapFill message is sent only in response to a resend request unlike a SeqReset-Reset message. However, from the 4.0 specs it seems that SeqReset-Reset message can always be used instead of SeqReset-GapFill message. Can you please give examples of any cases where it is preferrable to send SeqReset-GapFill message, and why.
>
> Thanx.
> Rajan.
>
>
>
>

Gap messages check the MsgSeqNum to ensure message are arriving in sequence.

Reset messages do not check MsgSeqNum and therefore will not produce a ResendRequest message.

Note: SequenceReset can only increase the MsgSeqNum.

Summary: You will use Gap messages most of the time because you need to recover the messages and don’t need to resend the system messages(heartbeat).

Charles Easton

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[ original email was from Dean Kauffman - dean.kauffman@tradeweb.com ]
Rajan,
The 4.2 spec clarifies the difference - “The Sequence Reset-Reset” mode should ONLY be used to recover from a disaster situation which cannot be otherwise recovered via ‘Gap Fill’ mode." You might want to look at Vol 2 pg 24 for Gap-Fill scenarious.

Dean Kauffman

> > I understand that SeqReset-GapFill message is sent only in response to a resend request unlike a SeqReset-Reset message. However, from the 4.0 specs it seems that SeqReset-Reset message can always be used instead of SeqReset-GapFill message. Can you please give examples of any cases where it is preferrable to send SeqReset-GapFill message, and why.
> >
> > Thanx.
> > Rajan.
> >
> >
> >
> >
>
> Gap messages check the MsgSeqNum to ensure message are arriving in sequence.
>
> Reset messages do not check MsgSeqNum and therefore will not produce a ResendRequest message.
>
> Note: SequenceReset can only increase the MsgSeqNum.
>
> Summary: You will use Gap messages most of the time because you need to recover the messages and don’t need to resend the system messages(heartbeat).
>
> Charles Easton
>