Biography:

One of their most recent publications is Chapter 1 - Introduction. Which was published in journal .

More information about Michael D. Duffy research including statistics on their citations can be found on their Copernicus Academic profile page.

Michael D. Duffy's Articles: (8)

Chapter 1 - Introduction

Publisher SummaryThis chapter provides an introduction to OpenVMS that is suitable for a wide variety of tasks. It can be used as a personal system, a multiuser timesharing system, a batch engine, a network server, or a network client, and it can serve several of these uses at the same time. OpenVMS is used extensively by hospitals and other medical facilities, by major stock exchanges and banks around the world, by one of the very largest Internet search engines, and by many Fortune 500 companies for which downtime would mean the loss of hundreds of thousands, or perhaps millions, of dollars per hour. In short, OpenVMS is used extensively where system reliability is crucial. Users of the OpenVMS operating system enjoy a feature many other systems claim, but few deliver:scalability. The high end of the OpenVMS performance line currently includes systems with multiple CPUs, several gigabytes of physical memory, and terabytes of disk capacity. On the other end of the spectrum are systems the size of two telephone directories stacked atop one another. OpenVMS can effectively manage the resources of a wide variety of machines, which in the next couple of years will certainly include even more impressive hardware models, both large and small. The chapter concludes that in many ways, OpenVMS is a more advanced system than many cutting-edge operating systems. Rather than remaining static, OpenVMS is continued to improve for the past two decades, incorporating features that make it an excellent choice for the most sophisticated modern applications.

Chapter 5 - Logging In and Out of the System

Publisher SummaryThis chapter outlines the steps necessary to establish a connection and log into an OpenVMS system. First, one must acquire a user account. If a user is using an existing OpenVMS system, the system manager will supply him a username and initial password. If the user has just installed OpenVMS on a computer, he/she should use the SYSTEM account and the password that is determined at installation time. If the user does not know what type of access he/she has, the system manager should be consulted. A user should read the entire sequence of events before trying it for the first time because the login sequence must be completed within a certain amount of time. Otherwise, it has to begin again. The chapter describes several connections methods:if user has a directly connected terminal; if user has Telnet access; if user has terminal server access; if user has a GUI-based workstation.

Chapter 7 - The User Environment

Publisher SummaryThis chapter discusses the OpenVMS user environment; how to work with files, directories, printers, and batch queues; and how to run programs and perform other common tasks. Most OpenVMS operations act on files, the primary unit of data storage. With few exceptions, all data processed by the system reside, at one time or another, in files. An understanding of files is essential to using most operating systems. Programs, letters, memos, pictures, audio clips, and just about any other type of data are stored in files. A file is a single logical unit on a computer storage device and is made up of records. OpenVMS supports many different file and record formats. Under OpenVMS, programs have the filetype .EXE. How you run them depends on the expectations of the program.

Chapter 12 - E-mail

Publisher SummaryThis chapter introduces the OpenVMS e-mail facility. In the early days of OpenVMS, the mail facility could send messages only to users on the local node or on a DECnet network, but it has since been enhanced to allow messages to be sent to or received from any Internet e-mail address. There are two ways to use OpenVMS mail. One is to use the MAIL facility directly on the OpenVMS system, either through a text interface or through the GUI. The other method is to use the OpenVMS computer system as an e-mail server for separate client systems, such as personal computers. The chapter describes both the approaches and also describes the traditional terminal-based interface to OpenVMS MAIL. Terminal interface allows user to send messages to and receive messages from other OpenVMS users on the DECnet network.

Chapter 16 - Your Personal OpenVMS System

Publisher SummaryThis chapter provides information to users who have acquired their own personal OpenVMS system. It provides brief explanation of how to start up and shut down their personal OpenVMS computers properly. It discusses control subsystem that usually takes the form of a program that is stored in the nonvolatile memory of the main computer and runs on the same CPU that executes the operating system. To start OpenVMS, it is necessary to give the appropriate instructions to the console subsystem. The console subsystem locates and loads that portion of OpenVMS dedicated to system startup, which, in turn, loads the remainder of OpenVMS. OpenVMS uses the SRM console. Many OpenVMS software products require a license to be installed before they are used. User must use the OpenVMS License Management Facility (LMF) to load the licenses onto their system. OpenVMS can run full-featured TCP/IP products, one can connect it to the Internet. To use OpenVMS system as an e-mail server, user must ensure that the SMTP server is not configured as an open relay.

Chapter 17 - The Process

Publisher SummaryThis chapter discusses process, which can be scheduled by OpenVMS, independently of other tasks. It discusses the internal structure of a process and explains how the virtual memory and scheduling mechanisms of OpenVMS act upon a process. OpenVMS maintains a list of processes that exist at any given time. When a user, log in, a process is created and when log out, it is destroyed. Each batch job executes as its own process, and many DECnet network operations execute as separate processes. A CPU executes one process at a time. A process has its own memory context. The concept of a memory context is essential to the idea of a process. One way to envision a context is to consider it to be a snapshot of the process, which can be saved while the CPU works on other things. The concept of a process context includes more than just a snapshot of its structure. Under OpenVMS, each process has its own memory, separate from the memory of other processes, which cannot be directly accessed by another process. OpenVMS constructs processes so that the first 2GB of each process's memory-addressing space is separate from that of all other processes. The OpenVMS virtual memory management subsystem is responsible for the allocation of physical memory among processes and provides the illusion of a 4GB address space to each process. The chapter describes the memory layout of a process and also discusses various states to processes that are assigned by OpenVMS.

Chapter 19 - Images

Publisher SummaryOpenVMS programs are known as executable images or just images, and the process of starting program execution is called image activation. Under OpenVMS, image files have the filetype .EXE. This chapter provides information to images that refer to the contents of the executable file:some sections of the file contain program contents exactly as they are to be laid out in memory. Hence, some sections of the executable file are exact images of their memory counterparts. Image executions are requested directly by using the DCL RUN command or a foreign command, and most other DCL commands invoke an image to carry out the requested action. For most images, activation includes steps that allow the inclusion of a debugger, image dump facility, or traceback facility. For security reasons, support for these features is disabled for some types of images, including installed images. Some images are simple, self-contained programs and require no further preparation. However, a simple main image may be linked against shareable or installed images, calling for additional preparation before being executed. The chapter describes shareable image that is a special type of image that allows several processes to use functions stored in a single image file. OpenVMS shareable images are roughly equivalent to dynamic link libraries (DLLs) as implemented within the Microsoft Windows environment. It also describes installed images, which is also called a known file.

Chapter 20 - The Files-11 File System

Publisher SummaryA file system is that part of an operating system that controls the storage and manipulation of files on media, such as disks. This chapter describes a file system supplied with OpenVMS:Files-11. Within the Files-11 design, there are two main specifications for the physical arrangement of data on a disk. They are ODS-2:for On-Disk Structure level 2, used for most of the history of OpenVMS and ODS-5:a newer disk structure that has been gaining popularity for the past few years. The OpenVMS file system provides support for several types of multivolume disk sets, including volume sets, shadow sets, hardware- and software-based stripe sets, and RAID arrays. The chapter discuses file system terminology and common file operations. It also discusses the file layout on disk:a new disk must be initialized before being used as a Files-11 volume. Initialization establishes INDEXF.SYS and the other reserved files. Since Files-11 is used on systems with many concurrent users, it must be able to satisfy a variety of requests from a variety of sources. At any given time, some users may be creating files, others may be deleting files, and yet others may be extending existing files. These are operations that must be serialized, because they move disk blocks between the allocated and free states.

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