ALET qualification

The address space where you can place parameters varies with the individual service:

You can place parameters in the primary address space in all service.
You must place parameters in the primary address space in some services.
You can place parameters in any address space in some services.

To identify where you can locate parameters in a service, read the individual service description.

Programs in AR mode that pass parameters must use an access register and the corresponding general purpose register together (for example, access register 1 and general purpose register 1) to identify where the parameters are located. The access register must contain an access list entry token (ALET) that identifies the address space where the parameters reside. The general purpose register must identify the location of the parameters within the address space.

The only ALETs that MVS™ services typically accept are:

Zero (0), which specifies that the parameters are in the caller's primary address space
An ALET for a public entry on the caller's dispatchable unit access list (DU-AL)
An ALET for a common area data space (CADS)

MVS services do not accept the following ALETs, and you cannot attempt to pass them to a service:

One (1), which signifies that the parameters are in the caller's secondary address space
An ALET that is on the caller's primary address space access list (PASN-AL) that does not represent a CADS

Throughout, this information uses the term AR/GPR n to mean an access register and its corresponding general purpose register. For example, to identify access register 1 and general purpose register 1, this information uses AR/GPR 1.