Single Side Update

Single Side Update messages provide an updated price and size for a single side of a Symbol. The side is denoted by the Side field. One Single Side Update message may reflect one or more updates to the inside book that were processed at the same time, but will only be done so in a way that can be arbitrated between A/B feeds.

Single Side Update messages come in two variants: Single Side Update Expanded (Short) and Single Side Update Expanded (Long). The Single Side Update Expanded(Short) message is used whenever possible, but the Single Side Update Expanded(Long) message is used when the Price cannot be represented by a Binary Short Price or the Quantity cannot be represented by an unsigned 16-bit integer.

If any All or None size exists on both sides at a price level at or better than the firm quote, it will be represented by a separate message.

For (C1 Only), if any customer firm size exists, the best customer firm quote will be represented as a separate message.