Job or Session?

A major difference between a session and a job is the difference between "right now" and "sometime in the future."

During a session, the computer attempts to execute your instructions as soon as it possibly can.

A job, however, executes your instructions in one of these two ways:

You can tell the computer when to begin executing a job--or you can let the computer decide the earliest opportunity for executing your job.

There are other differences between jobs and sessions.

During a session, your terminal becomes unavailable to you for the fraction of a second that it takes for the command to finish executing. As soon as the execution terminates, the computer shows you another prompt and waits for your next instruction.

However, there are commands and some special programs that require considerable time to finish executing. During the time that a command or program is executing, your terminal is unavailable to you. It could be unavailable for seconds, or even for hours. That can happen during some complex system administration tasks, such as backing up your files. It can happen, too, if the computer is using all of its resources to satisfy the needs of many users.

At such times, it is only natural to want for a way of recapturing the use of your terminal, or to defer the execution of some task until the computer is able to devote a larger portion of its resources to your work.

Jobs answer both requirements by running in the background, more or less out of sight. Indeed, when it does execute, your job will claim none of your time, nor will it "steal" your terminal from you. While a job is running, your terminal is free for whatever other work you might want to do. You can even tell a job when to run: hours, days, weeks, months, even as much as a year from now. You do not have to be at your terminal while a job runs.

There is a drawback, however. A session is called "interactive" because you and the computer are engaged in a "dialogue"--a conversation of sorts--during which you can issue any valid command and see the results almost immediately. You are free to change your mind, modify a command, and try it again. If the command or program that you are running prompts you to provide more information, you can enter the correct response then and there. Errors that occur give rise to error messages on your video terminal and permit you to analyze them and correct any mistakes.

Jobs, by contrast, are not interactive. When you send a job to the computer for processing, your ability to influence the job is usually confined to suspending the execution of the job (BREAKJOB jobnumber), resuming its execution (RESUMEJOB jobnumber), or terminating the job (ABORTJOB jobnumber).

	TIP: There are techniques for designing a job in such a way that the job will stop to prompt you for more information. A job of that sort, however, requires your presence at the terminal.

Starting jobs through HP Easytime/iX

Starting a job through HP Easytime/iX is accomplished through the Job Management screen. You will find information about starting jobs through HP Easytime/iX in the book Getting Started - HP 3000 Series 9X8LX (B3820-90003).

Starting jobs through MPE/iX Commands

Starting a job through MPE/iX commands involves using the STREAM command. For that reason, running a job is sometimes called "streaming a job." A loose analogy might be a pipe through which jobs "flow" on their way to some processing. At any time, there might be one or many jobs in the "pipe" on their way to processing.

The simplest way of starting a job is to enter something like this:

STREAM TAXJOBReturn

TAXJOB is some job file that you have created and saved to disk.

Do not confuse the STREAM command, which any user can execute, with the STREAMS command, which is available only to a user with SM or OP capability.

• STREAM sends a job to the computer for execution (puts it in the pipeline).

• STREAMS permits an operator or a manager to "open or close the pipe" for streaming jobs.

You cannot use the STREAM command until someone has executed the STREAMS command to permit the streaming of jobs.

You will find more details on the mechanics of starting a job in the book Task Reference - HP 3000 Series 9X8LX (B3813-90009).