The z/OS® Communications Server TCP/IP stack is a multiple-processor capable stack, which means that it can concurrently exploit all available processors on a system. Starting multiple stacks will not yield a significant increase in throughput.
In addition, running multiple z/OS Communications Server TCP/IP stacks requires additional system resources, such as storage, CPU cycles, and DASD. It also adds a significant level of complexity to the system administration tasks for TCP/IP.
For these reasons, it is suggested that in most cases you use the INET configuration, which supports a single TCP/IP stack. However, there are some special situations where running multiple stacks can provide a benefit. For example, you might want to run two separate stacks for intranet and Internet traffic.