The ICM performance is affected by the three important Oracle parameters PMON cycle, queue size, and sleep time.

PMON cycle - This is the number of sleep cycles that the ICM waits between the times it checks for concurrent managers failures, which defaults to 20. You should change the PMON cycle to a number lower than 20 if your concurrent managers are having problems with abnormal terminations.

Queue Size - The queue size is the number of PMON cycles that the ICM waits between checking for disabled or new concurrent managers. The default for queue size of 1 PMON cycle should be used.

Sleep Time - The sleep time parameter indicates the seconds that the ICM should wait between checking for requests that are waiting to run. The default sleep time is 60, but you can lower this number if you see you have a lot of request waiting (Pending/Normal). However, reducing this number to a very low value many cause excessive cpu utilization.

Purging Concurrent Requests

When the space in FND_CONCURRENT_PROCESSES and FND_CONCURRENT_REQUESTS exceed 50K, you can start to experience serious performance problems within your Oracle Applications. When you experience these space problems, a specific request called "Purge Concurrent Requests And/Or Manager Data" should be scheduled to run on a regular basis. This request can be configured to purge the request data from the FND tables as well as the log files and output files on accumulate on disk.

Adjusting the Concurrent Manager Cache Size

Concurrent manager performance can also be enhanced by increasing the manager cache size to be at lease twice the number of target processes. The cache size specifies the number of requests that will be cached each time the concurrent manager reads from the FND_CONCURRENT_REQUESTS table. Increasing the cache size will boost the throughput of the managers by attempting to avoid sleep time.

Analyzing Oracle Apps Dictionary Tables for High Performance

It is also very important to run the request Gather Table Statistics on these tables:
· FND_CONCURRENT_PROCESSES
· FND_CONCURRENT_PROGRAMS
· FND_CONCURRENT_REQUESTS
· FND_CONCURRENT_QUEUES.
Run the request "Analyze All Index Column Statistics" on the indexes of these tables. Since the APPLSYS user is the owner of these tables, so you can also just run the request Analyse Schema Statistics for APPLSYS.