Which API and version are you using? I'm assuming RFA 7.6.x or earlier given the group you posted in.
The rfa::sessionLayer::MarketDataItemEventEnum represents an event related to market data activity such as when you receive your initial data image and market data updates. The list of events is available within the Legacy section of the documentation:
You can also find example code segments within the Developers Guide.
This event is specifically related to the legacy message format: MarketFeed. The MarketFeed format is a text-based message format containing field/value pairs that is decoded using the TibMsg API. The basic idea is that you feed the raw message buffer into a TibMsg object and from there you can pull out the fields of interest. You can either use the .Get() method or pull out the fields using the TibField class. If you want to understand more, you can refer to the above screenshot and review the TibMsg programmers guide as well as review some of the examples.
All the above description is legacy reference and is no longer a strategic solution. Instead, TR replaced the Marketfeed format with the Reuters Wire Format (RWF) which is what OMM utilizes. The messages supported using this format have been completely rewritten to replace the legacy Marketfeed format.
Hope this helps.
Thanks much @nick.zincone.1 for the detailed explanation! Yes, We are using the 7.6.0.E1 API version.
Upgrade to the Latest Reuters API is next in our List. With TibMsg and TibField, we noticed that in the absence of Reuters Price value it returns 0.0 instead of null. Is this limitation is addressed in new Reuters Wire Format (RWF) which OMM utilizes Or it is something not considered as an issue from the point of view of Reuters API?
Yes, you can identify using our OMM market data APIs if a field is empty or blank if the data associated with a field is absent. You may also find it helpful to view the Webinar within the news section of the developer portal:
Hope this helps.