This section describes processes that have multiple dubbed tasks created by using the ATTACH system service. It describes how the first dubbed task in a process can be created and how to create additional dubbed tasks using ATTACH. It also describes how signals work in a process with multiple dubbed tasks created by ATTACH.
The first dubbed thread in a process can be created with the fork callable service or the exec or execmvs callable service, or by the first call to az/OS UNIX callable service from any task in the address space. Subsequent tasks can be created in the process with the ATTACH system service. Once a program running on behalf of the task calls a z/OS UNIX callable service, the task becomes dubbed. Every dubbed task is assigned an 8-character thread ID.
The mvssigsetup and sigaction services allow only one thread in a process to set up a signal interface routine (SIR) and signal catchers. When a process contains two tasks with signals unblocked, the signal is delivered to the task that called mvssigsetup.