Your program can create a data space, but it cannot own the data space. If the unit of work that represents the program is a TCB, that TCB is the owner of the data space, unless the program assigns ownership to another TCB. If the unit of work is an SRB, the program must assign ownership to a TCB. Because of this assignment of ownership, the owner of the data space and the creator of the data space are not always the same TCB.
The data space virtual area is available to programs that run under the TCB that owns the data space and is available, in some cases, to other programs.
When a TCB terminates, the system deletes any data spaces that the TCB owns. The system swaps a data space in and out as it swaps in and out the address space that dispatched the owning TCB. Thus, data spaces shared by programs that run in other address spaces must be owned by TCBs in non-swappable address spaces.
A data space can remain active even after the creating TCB terminates. When the program creates a data space, it can assign ownership of the data space to a TCB that will outlast the creating TCB. In this case, the termination of the creating TCB does not affect the data space.
Because access lists and data spaces belong to units of work, keep in mind the relationship between the program and the unit of work under which it runs. For simplicity, however, this chapter describes access lists and data spaces as if they belong to programs. For example, "a program's DU-AL" means "the DU-AL that belongs to the TCB under which a program is running".
