---
title: "FIX 5.0 SP2 EP299: SequenceReset <4> message – FIX Dictionary – Onix Solutions"
description: " "
---
# SequenceReset <4> message
## FIX 5.0 SP2 EP299
### Description
The Sequence Reset message has two modes: Gap Fill mode and Reset mode.
**Gap Fill mode**
Gap Fill mode is used in response to a [ResendRequest <2>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_2_2.html) when one or more messages must be skipped over for the following reasons:
- During normal resend processing, the sending application may choose not to send a message (e.g. an aged order).
- During normal resend processing, a number of administrative messages are skipped and not resent (such as Heart Beats, Test Requests).
Gap Fill mode is indicated by [GapFillFlag <123>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_123.html) field = "Y".
If the [GapFillFlag <123>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_123.html) field is present (and equal to "Y"), the [MsgSeqNum <34>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_34.html) should conform to standard message sequencing rules (i.e. the [MsgSeqNum <34>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_34.html) of the [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) GapFill mode message should represent the beginning [MsgSeqNum <34>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_34.html) in the GapFill range because the remote side is expecting that next message sequence number).
**Reset mode**
Reset mode involves specifying an arbitrarily higher new sequence number to be expected by the receiver of the [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-Reset mode message, and is used to reestablish a FIX session after an unrecoverable application failure.
Reset mode is indicated by the [GapFillFlag <123>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_123.html) field = "N" or if the field is omitted.
If the [GapFillFlag <123>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_123.html) field is not present (or set to N), it can be assumed that the purpose of the [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) message is to recover from an out-of-sequence condition. In [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Reset mode, the [MsgSeqNum <34>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_34.html) in the header should be ignored (i.e. the receipt of a [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Reset mode message with an out of sequence [MsgSeqNum <34>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_34.html) should not generate resend requests). [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Reset should NOT be used as a normal response to a [ResendRequest <2>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_2_2.html) (use [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Gap Fill mode). The [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Reset should ONLY be used to recover from a disaster situation which cannot be recovered via the use of [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Gap Fill. Note that the use of [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) - Reset may result in the possibility of lost messages.
**Rules for processing all Sequence Reset messages:**
The sending application will initiate the [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html). The message in all situations specifies [NewSeqNo <36>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_36.html) to reset to as the value of the **next** sequence number to be expected by the message recipient immediately following the messages and/or sequence numbers being skipped.
The [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html) 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 Resend Requests 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 [ResendRequest <2>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_2_2.html) may appear as [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-GapFill mode with [NewSeqNo <36>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_36.html) of 8, message 8, [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-GapFill with [NewSeqNo <36>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_36.html) of 10, and message 10. This could then followed by [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-GapFill with [NewSeqNo <36>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_36.html) of 8, message 8, [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-GapFill with [NewSeqNo <36>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_36.html) of 10, message 10, and message 11. One must be careful to ignore the duplicate [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-GapFill mode which is attempting to lower the next expected sequence number. This can be detected by checking to see if its [MsgSeqNum <34>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_34.html) is less than expected. If so, the [SequenceReset <4>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_4_4.html)-GapFill mode is a duplicate and should be discarded.
### Structure
| Tag | Field Name | Req'd | Comments |
| --- | --- | --- | --- |
| [Component Block - ](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/compBlock_StandardHeader.html) | Y | [MsgType <35>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_35.html) = 4 | |
| 123 | [GapFillFlag](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_123.html) | N | |
| 36 | [NewSeqNo](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/tagNum_36.html) | Y | |
| [Component Block - ](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/compBlock_StandardTrailer.html) | Y | | |
### Sample Messages
The `^` character is used to represent [`SOH`](https://en.wikipedia.org/wiki/C0_and_C1_control_codes#SOH) character.
```
8=FIXT.1.1^9=107^35=4^49=SellSide^56=BuySide^34=2^43=Y^52=20190605-17:09:11.496^122=20190605-17:09:11.496^1128=9^123=Y^36=4^10=134^
```
### Related Messages
- [Resend Request <2>](https://www.onixs.biz/fix-dictionary/5.0.sp2.ep299/msgType_2_2.html)
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