VMS Internals and Data Structures 2.2 1981

This document, "VAX/VMS Internals and Data Structures" (April 1981, Order No. AA-K785A-TE, for VAX/VMS V2.2), is a comprehensive manual detailing the internal workings of the VAX/VMS operating system.

Its primary objective is to explain the internal control paths and data structures used by the VAX/VMS executive, as well as how the operating system leverages specific VAX hardware features. It is intended for system programmers and other advanced users with a strong understanding of VAX-11 MACRO programming, VMS concepts, and VAX architecture, who wish to understand the OS at a deeper level for configuration, performance optimization, and application design. The emphasis is placed on the data structures manipulated by various executive components rather than detailed flow diagrams.

The manual is structured into eight main parts:

• System Overview: Introduces fundamental concepts such as processes, jobs, images, VMS layered design, and virtual address space layout.
• Control Mechanisms: Covers exception handling, system service dispatching, software and hardware interrupts, asynchronous system traps (ASTs), and error handling (including bugchecks).
• Scheduling and Timer Support: Explains process scheduling, interprocess communication, and system timekeeping.
• Memory Management: Describes data structures and operations related to the pager and swapper, alongside virtual memory system services.
• Input/Output: Details VMS device drivers and I/O system services, including the QIO request mechanism.
• Process Creation and Deletion: Outlines the lifecycle of processes, image activation, and termination within interactive and batch environments.
• System Initialization: Covers the bootstrap procedures (VMB, SYSBOOT) and powerfail recovery sequence.
• Miscellaneous Topics: Discusses synchronization techniques, dynamic memory allocation, and logical names.

A crucial note within the preface highlights that the detailed internal operations and data structures described are specific to VAX/VMS V2.2 and are subject to change in future releases, advising that privileged applications relying on these specifics must be retested with each new version.