You can configure the Network Server to use a specific number of threads to handle connections. You can change the configuration on the command line.
The minimum number of threads is the number of threads that are started when the Network Server is booted. This value is specified as a property, derby.drda.minThreads = <min>. The maximum number of threads is the maximum number of threads that will be used for connections. If more connections are active than there are threads available, the extra connections must wait until the next thread becomes available. Threads can become available after a specified time, which is checked only when a thread has finished processing a communication.