When you start several TCP/IP stacks under OMVS, you are using the Common INET (CINET) PFS. Users and jobs can optionally establish affinity to a single stack, or they can allow CINET to choose a stack. If stack affinity is not set, CINET replicates the socket() command to all stacks attached to it. If a job or user does not have READ access to any of the attached stacks, RACF® might generate audit failure messages for those stacks. As long as at least one stack accepts the socket() command, CINET will return success to the application. CINET then routes subsequent commands on that socket to one or more of the stacks that accepted the socket() call. For further information on CINET, see z/OS UNIX System Services Planning.