The Shareplex commands are used for monitoring what is gathered by Capture process from source database, in terms of redo log sequence number and offset. The command for monitoring is show capture detail. At times it is observed that while the value of redo log sequence number and offset keeps incrementing after each issuance of the command, the number of messages and backlog in Capture queue remains unchanged. This solution explains the reasons behind this.
It is possible to see Capture keep processing and advancing (as seen in the statistic about redolog sequence # and offset processed by it) even while no new messages are gathered in the Capture queue. It is quite possible that Shareplex is not configured to replicate all the changes that occur on the source database. This is especially true when not all tables on source database are a part of the config file. So the Capture process will not gather every change that is contained in the redo log. Consequently while the redolog sequence # and offset will keep incrementing as the database runs, it is possible at times to see no new messages accumulating in Capture queue for some period of time.