Shareplex source shows a large backlog on Reader.
Shareplex source may have been shutdown for an extended period of time.
When Shareplex is started again it will read in the redo logs created since it was last up. These logs will quickly be read into the capture queue.
Reader will then show a large backlog when running sp_ctrl> qstatus. (This is normal behavior)
The backlog may appear to reduce significantly and then increase by the same amount again. This will most likely be due to reader moving into pass 2.(This is normal behavior) To monitor reader statusand what pass it is in run - sp_ctrl> show read internal
Wait for backlog to decrease.
Please also see the following solutions: SOL18490, SOL17453,SOL26849