Introduction to the New Mainframe: z/VSE Basics

Chapter 3. z/VSE overview 93

– System Directory List (SDL)

The SDL is the directory of the phases to be loaded into the SVA (VLAs)

during the system startup.

– Supervisor

In this area is the

low core and a part of a control program that coordinates

the use of resources and maintains the flow of processor operations.

The low core is a common area of virtual storage starting from address

zero in every address space. There is one unique Low Core for every

processor installed in a system. The Low Core is 4k prior to z/VSE 4.1 and

8K in z/VSE 4.1. It maps architecturally fixed hardware and software

storage locations for the processor. Because there is a unique Low Core

for each processor, from the view of a program running on z/VSE, the

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