Resolution:
The correct setting for your environment should be determined based on your CPU and Memory resources.  Please note that specifying a very high value can cause resource contention, CPU thrashing, or an increase in latency due to a large number of messages in the queue which in turn can lead to time outs similar to those you are experiencing. At the same time, specifying too low value can cause higher memory usage and lower engine throughput as some CPU resources remain under utilized.

We recommend that the CPU and memory resources should be measured under typical processing loads to determine if the default value needs to be modified. If the engine throughput has reached to max but the CPU and memory are not being fully utilized, then the ThreadCount can be increased which should have a positive effect on the overall throughput.

For more information please refer to ”TIBCO BusinessWorks™ Administration Software Release 5.4/
Chapter 10 Performance Tuning : Performance Considerations/Thread Count. “

How to determine the value of ThreadCount?