A number of Oracle bugs (#716771, #375315, #668155, #808970, and so on) can cause a shared server (MTS) to be converted into a dedicated server. This normally happens when db_link is used.
Spotlight raises an alarm when many shared servers are converted, leaving too few shared servers to meet the demand. Converted shared servers have a status of WAIT(RECEIVE) in v$shared_server.
You may need to apply the latest patch to the database.
About shared servers and dedicated servers
Both shared and dedicated server processes execute Oracle server code on behalf of database user processes. However, while shared servers can serve any client request, each dedicated server can serve only a particular user process.