This access log field is a new field that's been added starting in 6.2 version, and provides the operation performed. For example when a user is using Facebook and is posting a message:
So the 'operation' is the x-bluecoat-application-operationfield.
However you need to use BCWF as your content filter database. Other content filter databases such as websense cannot be used, and will record the value as 'Unavailable' or '-'.