PriorityIndicator (FIX tag 638)

intFIX 4.4

PriorityIndicator (tag 638) is an int field defined in FIX 4.4. It appears in 1 message type, always optionally. It is an enumerated field with 2 defined values.

At a glance

Tag: 638
Name: PriorityIndicator
Datatype: int
Dialects: FIX 4.4
Messages: 1
Valid values: 2

What the specification says

Indicates if a Cancel/Replace has caused an order to lose book priority

Descriptions are quoted from the FIX Orchestra sources under the Apache 2.0 licence.

A real message using tag 638

ExecutionReport · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	139
35	MsgType	8	Execution Report
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
37	OrderID	ORD-10042
17	ExecID	EXEC-88117
150	ExecType	0	New
39	OrdStatus	0	New
54	Side	1	Buy
151	LeavesQty	0
14	CumQty	1000000
6	AvgPx	1.09215
638	PriorityIndicator	0	Priority Unchanged
10	CheckSum	046

Edit and decode it yourself

Shown with | separators for readability. On the wire FIX uses SOH (0x01), an invisible control byte — and because BodyLength and CheckSum are computed over the actual bytes, the two forms have different checksums. Both are valid and both decode here.

Open in the full decoder →

Generated from the FIX 4.4 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Valid values

A value outside this list is not a parse error — the message still decodes — but validate() reports it as validate/value-not-in-enum.

Value	Meaning	Symbolic name
0	Priority Unchanged	PRIORITY_UNCHANGED
1	Lost Priority as result of order change	LOST_PRIORITY_AS_RESULT_OF_ORDER_CHANGE

Where tag 638 appears

Requiredness is a property of the message, not of the field: the same tag can be optional in one message and conditionally required in another.

Message	MsgType	Requiredness	Where in the message
ExecutionReport	8	Optional	directly on the message body

Wire format

A whole number, optionally signed. Leading zeros are legal on the wire and are preserved in the raw value. @boarteam/fix parses the value as a number and reports parse/invalid-int when it does not lex as one; the raw string is kept either way.

Read tag 638 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix44";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const priorityIndicator = message.fields[638]?.raw;// e.g. "0" — Priority Unchanged// The dictionary also carries the labels:const label = fix.dictionary  .fieldByTag(638)  ?.enumValues?.find((e) => e.value === priorityIndicator)  ?.description;

Decode this in your own code

The same engine that produced the decoded example above is an Apache-2.0 npm package with zero runtime dependencies. It runs in Node and in the browser, and parse() returns problems as data instead of throwing.

npm i @boarteam/fix @boarteam/fix-dict-fix44

Try the decoder Source on GitHub