How an ALET connects a program to a hiperspace

An ALET is an index to an access list. An access list is a table where each entry represents an address space, data space, or hiperspace that programs can access. Each program has two access lists: a primary address space access list (PASN-AL) and a dispatchable unit access list (DU-AL).

Each address space has one PASN-AL. It is available to any program that has that address space as its primary address space.
Each TCB and SRB has one DU-AL. It is available to any program that the TCB or SRB represents.

To use one of these access lists, the program needs the ALET that indexes the access list. It uses the ALET as input on the HSPALET parameter on HSPSERV.

Using access registers describes ALETs for data spaces and address spaces; for an illustration of a DU-AL and PASN-AL, see Figure 1. Creating address spaces 6 limits its discussion to ALETs for hiperspaces.