If there is parallel concurrent processing enabled then there might be the case that once we stop down the concurrent managers it will not come up when trying to start .
 
Error
 
We may find the below error in the manager log which will state that manager is already running.
 
Routine &ROUTINE has attempted to start the internal concurrent manager.  The ICM is already running.  Contact you system administrator for further assistance.afpdlrq received an unsuccessful result from PL/SQL procedure or function FND_DCP.Request_Session_Lock.
Routine FND_DCP.REQUEST_SESSION_LOCK received a result code of 1 from the call to DBMS_LOCK.Request.
Possible DBMS_LOCK.Request resultCall to establish_icm failed
The Internal Concurrent Manager has encountered an error.
 
Cause
 
This is occoured due to locks in the Database.
 
Solution
 
1.Please use the below query to find the culprit SID .
 
select * from gv$session where program like '%ICM%'
 
2. Kill the SID and restart the Concurrent managers.
 
Oracle Note Id for more reference:Concurrent Processing – The Concurrent Manager Fails to Start on GSM Enabled Due to DBMS_LOCK.Request ResultCall Failed to Establish ICM [ID 245563.1]