If the concurrent manager is not responding and there are lot of pending request from long time then those request can be killed from the backend using the following query.
SET phase_code = ‘C’, status_code = ‘D’
WHERE status_code =’Q’ OR phase_code = ‘P’
AND REQUEST_ID = ;
You can kill all the long running requests.
Also one more option that can be done is login as apps/apps. Also we can make the internal manager to work like a CRM by setting the profile option
Internal Manager: work like CRM to yes.
Concurrent: Use ICM is the profile name
If u r getting Target node/queue unavailable in status column then in the manager –> define form check the Conflict resolution manager node. It should be set to correct node value. Set it to correct value and bounce the CM. By default this value is never set. It will take the node from FND_NODE table.