| Base Type | none |
A UserRefNum is an unsigned numeric. For a given OUCH port, the UserRefNum is used as a transaction identifier, and must be both unique and strictly increasing throughout the trading day. The system ignores new order requests identified with UserRefNums lower than the last one processed, assuming they are retransmissions.
Client however has an option to multiplex their order flow via the use of an optional tag UserRefIdx. When this tag is present the UserRefNum is then assumed to be linked to an “order flow channel” specified by the UserRefIdx and the above rules regarding the use of UserRefNum are applied only within this “order flow channel” instead of the port globally.
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