You can configure the number of servant threads in the workload profile for the server. To calculate the number of threads for each profile setting, you can use a formula based on the number of available processors.
For more information, see the Network Deployment (z/OS), Version 8.0 > Tuning performance information
in the 
WebSphere® Application Server Information
Center.
Take care when allocating threads to the IBM® Business Process Manager or WebSphere Enterprise Service Bus server. On z/OS®, there are standard thread settings for ISOLATE, IOBOUND, CPUBOUND, and LONGWAIT, which must be examined based on the workload.
To set the workload profile, open the administrative console and navigate to Servers > Server Types > WebSphere application servers > server_name > Container Settings - Container Services - ORB Service > z/OS additional settings.