Powering Up the Computer

The CPU is normally powered up first; then one by one, each of the I/O devices is turned on. This is done to prevent a sudden surge of power that might overload the circuits. With the computer system powered up, you can then proceed to IPL the system.

Booting the System

Anytime the system loses power, is shut down, or becomes disabled because of a system crash, it usually needs to be rebooted or initial program loaded (IPLed). A system crash is the result of a hardware, software, or ^{operation problem:} a malfunction in the CPU, a programming error from which the operating system could not recover, or an operator error caused by an incorrect response to a message. Booting most systems resets all status indicators and reloads the supervisor (the executive-system program along with other resident routines) into the CPU memory. The manner in which the system is booted depends upon the computer system used and the software included in its operating system. Many of the larger mainframe computers store their operating systems on disk, and this disk is referred to as the SYStem RESident (SYSRES) pack. Once the disk unit with the SYSRES pack is in a ready status, you can then boot the system. Some systems are so simple to boot that all you need do is depress the start (or load) button on the CPU (or master console) and enter the date and time on the console keyboard. Some of the more complex systems may require you to take additional steps\assigning various I/O devices, partitioning (sectioning off) memory, and so on. It is because of these differences that boot procedures are well documented with each step explained to the point that anyone, even someone unfamiliar with the system, could follow the step-by-step directions.

Computer Diagnostics

Computer diagnostics are of two types: those that are run when the computer is booted (called internal diagnostics), and those that can be run from a peripheral device (called external diagnostics).

INTERNAL DIAGNOSTICS.\ Internal diagnostics are performed when the computer is booted and are designed to test the computer hardware. They return a pass/fail result to the operator. Some of the internal diagnostics are designed to test all or selected sections of the computer. An example of an internal diagnostic test is the power on-self test (POST), that checks the components upon power on.

EXTERNAL DIAGNOSTICS.\ External diagnostics can be loaded into the computer from a peripheral (disk or magnetic tape unit) but initiated and

controlled by the computer. These diagnostics are very thorough and offer the option of testing all or specific sections of a computer. They are more comprehensive than the internal diagnostics.

RESPONDING TO MESSAGES

Unless you respond correctly to a system- or program-generated message, CPU time can be lost, the wrong program options can be executed, and the system can even become disabled. As a console operator, you are the most important part of a team effort that makes

computerized procedures successful. It is true that while complex operating systems make it easier for you to perform various tasks, correct responses to messages ^{are just as critical.} Never second-guess a response. Always refer to the proper documentation to determine ^{the response needed.} Manuals provided by the manufacturer, operator's manuals, and error message manuals should be located as near to the console as

possible for your convenience.

Basically, you will be concerned with two types of messages: system-generated messages and program-generated messages.

System-Generated Messages

System messages are generated by the operating ^{system software.} To be more specific, it is the executive-program (the supervisor) that is responsible for monitoring and allocating the resources of the system, and also for communicating with you, the operator.

While carrying out the instructions of an applications program or a utility program, the computer is in a program or problem state. While in this state, interrupts occur that return control of the system resources to the supervisor. When this occurs, the computer is in the supervisor or control state.

When an interrupt occurs, a message to the console operator may be displayed to indicate either a normal or abnormal condition. Some messages require a response on your part; others do not. "File XXX now being loaded," or "PAYROLL1 completed (EOJ)" do not require a response. Other messages, like "Printer Not Ready," or "No volume label found on pack XXX999," or "Insufficient memory allocated for job XXX" do require a response on your part.

You may be asking yourself, how do I know what occurred, and how do I respond to a system-generated ^message? YOU FOLLOW PROCEDURES! Most messages are coded, and you use this code to lookup the meaning of the message displayed. These types of messages are normally found in the software manuals supplied by the manufacturer. As you become more experienced, you will quickly become familiar with the different types of messages and be able to determine the origin of the message just by looking at the identifying codes.

Program-Generated Messages

Program-generated messages are those messages that are displayed by the program as the result of the programmer wanting to inform you of an available option or wanting you to supply data. The program might display a message such as "Enter expiration date," or "Option 1 to edit data, Option 2 to update file," or "Load four-part paper in printer."

Whenever a program message is displayed that requires a response, the run book/sheet along with the documentation (operator's manual, run manual) provided by the programmer should explain each and every response or option available and how you are to respond.