This problem is fixed in 11.3 SP3 and is documented in the release notes
Unable to Add a New Server Connection in CA WA Desktop Client Due to Deadlock
When you add a new server connection in CA WA Desktop Client, the connection gets timed-out after 30 seconds with the following error message:
20140708 13:54:01.157 [ws:connections] [INFO] WSS_reactor_8: Connection
In this issue, the scheduler thread acquired a lock on the RelationalDatabaseManager object and waited for the database connection. At the same time, the workload processing thread held the database connection and waited for the RelationalDatabaseManager object. Hence, the server moved into a deadlock and the database connection could not be released to the database connection pool.
This issue is fixed.
If you are not at SP3 the Upgrade patch 11.3 SP3 RO76709
then follow by the 11.3 SP3 Cumulative patch RO89278
and Also, the Desktop Client patch WIN-CUMULATIVE R11.3SP3 RO89279 .