How many rows are in FND_CONCURRENT_REQUESTS and FND_CONCURRENT_PROCESSES tables?
Depending on the specification of the system it has been seen that when tables reach above 3000-4000 rows, the performance begins to diminish, however, there could be 30000-40000 rows in the tale before the performance begins to degrade. You may want to run the Purge Concurrent Request and/or Manager Data on a regular basis, dependant on the amount of requests being run. The Purge Concurrent Requests job can be used to purge: Requests, Mgr logs, and All requests depending on what is chosen. Use the following options: Enter = All, Mode = AGE, Mode Value = 15 The std.mgr log continuously grows where it may good to archive it regularly.
