OpenVMS System Concepts and Architecture
OpenVMS is a multiuser, multiprocessing operating system built around a privileged kernel, a layered set of system services, and a command interface (DCL). The candidate must know the privilege modes - user, supervisor, executive, and kernel - and that each higher mode grants access to more of the address space and to privileged instructions. The process structure is central: each process has a P1 (per-process program) region, a P2 (per-process control) region, and shares the systemwide S0/S1 space. The Process Control Block (PCB), Job Information Block (JIB), and Process Header (PHD) are common exam targets; know that the PCB lives in system space and the PHD holds the working set and page tables.
Understand the distinction between images and processes: an image is an executable program mapped into a process, while a process is the execution context. Logical names provide a name-translation layer across four tables (process, job, group, system), searched in that order - a classic trap is assuming system logicals win; they are searched last unless the name is in a privileged table.
Traps: confusing a subprocess (spawned, shares nothing but inherits some context) with a detached process; assuming kernel mode equals the CLI; and mixing up the roles of JIB (accounting, group) versus PCB. Also be ready for questions on the boot driver, the system disk concept, and how SYSGEN parameters like MAXPROCESSCNT affect the system.
Rule of thumb: when a question asks "which table is searched first," answer process table; when it asks where a structure lives, remember per-process control data is in P2, shared kernel data in S0/S1.