HP 3000 Manuals HP 3000 Manuals
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:
* at some future time that you specify
* as soon as the computer has sufficient time and resources
available
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.
* The SHOWJOB command displays sessions as #Snnnn, where nnnn is the
session number.
* Sessions are interactive. You start an interactive session by
logging on with HELLO and continue your dialogue with the
computer, entering commands or running programs as you need them.
* The SHOWJOB command displays jobs as #Jnnnn, where nnnn is the job
number.
* Jobs are not interactive. You start a job during a session by
entering the STREAM command, followed by the name of a job file
that contains a list of commands. Then you continue with your
session, entering commands or running programs as you need
them--or perhaps you log off and go home for the evening.
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).
________________________________________________________________________
|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).