BDT runs in its own address space. A JES complex may have one or more BDT address spaces. Each processor in the complex may have one or more BDT address spaces. A complex with multiple BDT address spaces is called a poly-BDT complex. Figure 1 and Figure 2 show examples of poly-BDT complexes.

Figure 1. A Poly-BDT complex with BDT address spaces in the same processor

Figure 2. A Poly-BDT complex with BDT address spaces in different processors

A good use for poly-BDT complexes is to separate test work from production work. Figure 3 illustrates such a situation. In the figure, complexes A and C are poly-BDT complexes. They each have an address space for daily production work and another address space for testing (such as testing newly written user exit routines) and for training operators and users. By separating testing and training from the production work, a complex reduces the risk of disrupting its production work.

Figure 3. Poly-BDT complexes with separate test and production systems

If you want to estimate the storage required for each BDT address space, see Virtual Storage Required for the BDT Address Space.