mastering the as/400, third edition, author jerry fottral 1 week 2 the system the as/400 is a...

Mastering the AS/400, Third Edition, author Jerry Fottral

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Week 2The System

• The AS/400 is a multi-user, multi-tasking system -- a system on which many users can perform many tasks concurrently.

• The basic unit of work on the AS/400 is a job -- generally a unit of work, including all programs, files, and instructions necessary to perform that work.


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Week 2Sub Systems

• All jobs are run in areas of the computer called Sub systems. A Sub system is where the system brings together the resources needed to process work.– Sub system characteristics determine how the

system uses resources within the Sub system.

– The AS/400 operating system supports multiple Sub systems that can be User-defined, each having a separate Sub system description.


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Week 2Sub Systems (continued)

• Some attributes of Sub systems whose values are defined in the Sub system description include:– Sub system name

– How many jobs can run in a Sub system at one time

– Which storage pools the Sub system will use

– Which job queues the Sub system will work from


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Week 2Sub Systems (continued)

• Different Sub systems are necessary because of the many different types of jobs with different characteristics and often conflicting needs.

• The system administrator can tailor the existing Sub system descriptions and create new Sub systems to handle the needs of different types of jobs.

• Within Sub systems, individual jobs can be prioritized to begin execution sooner or later and, after they begin, can be given a higher or lower runtime priority.


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Week 2Types of Jobs

• On the AS/400 there are only two types of ‘jobs’ that can be initiated on the system. In general, the two types are:

–Interactive

–Batch


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Week 2Types of Jobs (continued)

Interactive Job:

• Begins when a user signs on to an AS/400

• Terminates when the user signs off the AS/400 or the job has ended

• Runs in conversational mode (i.e., dialogue of sorts between user and program, utility, or operating-system function)


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Interactive Job (continued):• Because of the conversational mode (back-and-

forth nature of interactive jobs), any such requests could lock up the workstation keyboard until the request is completed.

• It is advisable to direct job requests to the appropriate Sub system for that job – either to run Interactively or submit them as batch jobs.


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Batch Jobs:• Can execute without user intervention• Do not require data or any other information to be

input through the workstation once they have started

• Are sent to a job queue until they can begin execution. A job queue is a staging area, managed by the Sub system, where batch jobs wait in line for their turn at processing.


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Batch Jobs (continued):

• Each batch subsystem can execute only a limited number of batch jobs concurrently.(This is programmable).

• Depending on the settings, a batch job can start right away or wait it’s turn in the queue.


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Batch Jobs (continued):• A typical batch job submission would be a

report program or a program compile.• If such a program were run interactively,

the DASD (Direct Access Storage Device, or hard disk) access time required could cause the program to run for a long time, locking up the interactive session.


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• To minimize disruption of work flow, certain tasks during an interactive session can be sent as batch jobs --– Programmer could submit a compilation or

report as a batch job from the interactive job– While the submitted job runs in a batch

subsystem, the programmer could go on to other tasks.


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• An active job can be identified by the Qualified Job Name. A Qualified Job Name is made up of three distinct parts: - Job Name > based on the Terminal I.D. - User I.D. > The User I.D. that initiated the job. - Job Number > assigned by the system (For a batch job it is the program name)


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Week 2OS/400

• OS/400 is the AS/400’s operating system• It is a robust, complex, functionally rich set

of programs– It Controls traditional computer system

functions.– It Incorporates features that normally require

separate software components– It supports two other operating systems –

System/36 and System /38


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Week 2OS/400 (continued)

All AS/400s are shipped with basic OS/400 support, including predefined system settings for work management functions


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OS/400 is an object-based operating system:An object is anything on the system that has

a name and takes up space in storage.A large number of objects are supplied by

IBM through OS/400, and they typically have names beginning with Q. Other objects usually are named according to shop naming convention.

The system locates an object by its name.


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Objects are grouped into types, and an object type determines how the object is used on the system.

Common types include:*PGM - Programs*FILE - Files*CMD - Commands

Other types also include user-profile objects and subsystem-description objects.

Object type is always assigned by the system and is determined by the command used to create the object.


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Week 2Control Language

OS/400 provides a single, consistent user interface to its functions through Control Language (CL) commands.

• CL is flexible, powerful, and allows direct access to OS/400 functions.

• More than 1,500 commands are available.

• Each command is an object on the AS/400.


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Week 2Control Language (continued)

Most CL commands consist of a command name and one or more command parameters.

A Command Parameter has an associated value, specified along with a command, that controls and limits the operation of the command and names the files, programs, or other objects the command will work on.


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Week 2Control Language (continued)

Individual commands can be entered on a command line.

A command line is a line beginning with the symbol ===> that appears near the bottom of certain types of display screens.


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Week 2System Values

System values are control and configuration attributes that let you customize certain operating-system functions.– They define critical aspects of the environment and

general rules that jobs must follow.

– They are not objects.

– They describe characteristics of the system that can be displayed or changed with CL commands.

– Many come preset or others need to be set.


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Week 2User Profile

User: any person who is signed on to the system. Each user requires a user profile.

User profile: identifies a user and describes the user’s authority; the profile is the source of several operational characteristics of that user’s job and defines:

• user class (e.g. programmer, system operator)• special authorities• initial program to execute• group profile


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Week 2User Profile (continued)

The two user-profile values necessary to sign on are:

user name (or user ID)(1-10 characters long; security administrator determines its value

according to standards of the installation; user name may be simple first initial and last name combination or more symbolic code such as department; the user name or user ID must match the name of user-profile object or sign-on attempt will fail)

password(must match the current password stored in the corresponding user

profile)


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Week 2User Profile (continued)

Sign-on screen:

Upper right area of screen shows information identifying system, subsystem, and display device (or display station).

A display device is the workstation hardware (monitor and keyboard) that you use to communicate with the system.


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Week 2User Interface

The AS/400 Main menu:• Most AS/400 interactive jobs begin by displaying

the Main menu.• This menu is the highest-level task-oriented menu

on the AS/400.• It can be the starting point to define a menu path.• Menus are connected in such a way that a menu

choice at a higher level can take you to a lower-level menu.


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Week 2Menu Screens

Primary sections of a menu screen:• Screen header (includes menu ID--the menu object

name, menu description, and system name)

• Numbered list of menu options• Selection or command line, indicated by

===>• List of active function keys (and below this list

are: a message line showing the IBM copyright notice and a status line showing cursor coordinates)


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Week 2Menu Screens (continued)

From a menu display, you can:– Type and enter a menu choice and go on to the

next screen– Ask for Help– Type a CL command and either prompt for

parameters or run the command– Use a function key


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Week 2Menu Screens (continued)

To create a library, take the menu path to:DATA menu

From the DATA menu, you can take choice 2 (Libraries) by typing a 2 on the command line and then pressing Enter. This takes you to the LIBRARY menu.

The system displays an entry screen to request information from a user.


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Week 2Entry/Command Prompt Screens

• Note different heading -- Create Library (CRTLIB) is the name of a CL command followed by its AS/400 abbreviation in parentheses.

• The entry screen does not identify the system--you see a list of command parameters.

• A list of active function keys is displayed.


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Week 2Entry/Command Prompt Screens

Command prompt screen:

Is an entry screen; you need to enter required parameter value(s). When you enter these, e.g., OPS234SB for Library name of the CRTLIB command, the system can create a library. Thus the system prompts for a parameter value to run a command, and the screen is referred to as a command prompt screen (one kind of entry screen).


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Week 2Entry/Command Prompt Screens (continued)

To request additional parameters:Press function key F10

The Create Library (CRTLIB) Command Prompt Screen appears and provides:

• Description• Entry field showing parameter’s current value, if

any• List of valid values (for most parameters)--to view

the entire list, position cursor on the line containing the parameter in question and press Prompt function key F4.


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Week 2Entry/Command Prompt Screens (continued)

Required parameters:– Value must be provided to run a command.– Always appear as empty input fields at the top

of the command prompt parameter list.

For other parameters, use the default values provided, or you can type over any default value you need to change.


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Week 2Using Help

Information screens:

• Provide information that you request and provide a way back to where you were when you asked for the information.

• Help screen is a good example: the Help key is F1.


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Week 2Field or Context-Sensitive Help

General (Field) Help or Specific (context-sensitive) Help:

When you are requesting information about a particular area on a screen, you are requesting what is referred to as General Help or Specific (context-sensitive) Help.

Information window appears -- which can be enlarged by pressing function key F20 or cancelled by pressing function key F12.


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Week 2Extended Help

To access more information about the field Help window screen, press function key F12 for extended Help. You would see command parameters, for example, and their possible values, parts of the screen, and any entry fields or options available on screen.

mastering the as/400, third edition, author jerry fottral 1 week 2 the system the as/400 is a...

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