chapter07 batch and jes slides

7/30/2019 Chapter07 Batch and JES Slides

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Introduction to the new mainframe

Chapter 7: Batch processing and the Job EntrySubsystem (JES)

Copyright IBM Corp., 2006. All rights reserved.


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Chapter 7 objectives

Be able to:

Give an overview of batch processing and

system.

Explain how the job entry subsystem

governs t e ow o wor t roug az/OS system.

Copyright IBM Corp., 2006. All rights reserved. 2


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Key terms in this chapter

a c process ng

execution

initiator

proce ure

purge

queue

job

job entry subsystem (JES)

spool

symbolic reference



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What is batch processing?

Much of the work running on z/OS consists of programs

called batch jobs.

Batch processingis used for programs that can be

With minimal human interaction

At a scheduled time or on an as-needed basis.

After a batch job is submitted to the system for execution,there is normally no further human interaction with thejob until it is complete.



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What is JES?

In the z/OS operating system, JESmanages the input and

output job queues and data.an es e o ow ng aspec s o a c process ng or

z/OS:

Schedules them for processing by z/OS

Controls their output processing



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What is JES? (continued)

z/OS offers two types: JES2 and JES3

Some important differences, but both JES2 and JES3: ccept and queue jobs submitted for execution

Queue jobs for an initiator-- a JES program that requests the nextob in the ueue

Accept outputfrom a job while it is running and queue the output

Can print the output, or save it on spoolfor an output manager toretr eve.



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What is JES? (continued)



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Batch flow (simplified)

rocess ng

InitiatorJES

-

- Execution- Cleanup

SPOOLSPOOL

n a or

-Allocation- Execution

submit

-


Printer


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What is spooling?

Spoolingis a method for queuing and holding data for input

or output.uses one or more s a a se s or spoo ng.

Input jobs and printed output from many jobs are stored in.



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What an initiator does

To run multiple jobs asynchronously, z/OS uses

initiators to:

Ensure that single-user devices (tape drives) are allocatedcorrectly

Find executable programs requested by jobs Clean up after the job ends and request the next job

Preventing two users from accessing the same data at

is one of the defining characteristics of the operatings stem.



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Symbolic references to files

rather than actual file names.

The use of symbolic references provides a namingredirection between a data set-related name used in aprogram and the actual data set used during execution

of that program.



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How a symbolic file system is used

DDNAME DSNAME

=

program JCL for JOB

READ FILE=XYZ

...

//XYZ DD DSNAME=MY.PAYROLL MY.PAYROLL



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How a symbolic file system is used (continued)DDNAME DSNAME

OPEN FILE=XYZ

READ FILE=XYZ

program JCL for JOB

...

CLOSE FILE=XYZ

//XYZ DD DSNAME=DIV1.PAYROLLDIV1.PAYROLL



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JES, job management, and JCL

Job control language (JCL) is the language used by a

batch job to request resources and services from the.

Through JCL, you specify:

.

Which resources (programs, files, memory) and services areneeded from the system to process your program.

The use of JCL is covered in detail in the next module.



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Related actions with JCLIT USER ACTIONS SYSTEM ACTIONS

Determinethe need

and

characteristicsof the Job

Create

the JCL

Submit

the Job

JES interpretsJCL and

passes it toz/OS initiator

z/OS

manageseach step

of execution

SystemMessages

JES collectsUser

JES printsoutput

the output andinformation

about the Job

andinterprets

output



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SpoolingJCL

program

22read

//DD1 DD *

...............

data

//DD1 DD *

...............

data

//DD1 DD *

...............

data

11JES

spool

/*

//DD2 DD SYSOUT=A

...............

/*

//DD2 DD SYSOUT=A

...............

/*

//DD2 DD SYSOUT=A

...............

SYSOUT 44

JES



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Two-step job

First step

Updates MasterMaster

Second step

Program Program

Tape PrinterMaster



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Job flow through the system

During execution, a job goes through the following

phases:

Conversion

Processin

Output Print (to hardcopy or a console display)

Purge



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Phases of job flow: input

JOB

CONVERSIONQUEUE

INPUT CONVERSION PROCESSING HARD-COPY PURGEOUTPUT

JCL & SYSIN

SPOOLSPOOL



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Phases of job flow: conversion

EXECUTIONQUEUE

CONVERSIONQUEUE


JCL

SPOOLSPOOLDISKDISK



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Phases of job flow: executionJOB

OUTPUTQUEUE

EXECUTIONQUEUE


SYSOUTSYSIN

SPOOLSPOOLDISK



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Phases of job flow: output and hardcopy

JOB

PURGEQUEUE

HARD-COPYQUEUE

OUTPUTQUEUE


SYSOUT

NON-PRINT/PUNCHOUTPUT

SPOOLSPOOL

DISKDISK



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Phases of job flow: purge

JOB

PURGEQUEUE


SPOOLSPOOL

DISKDISK



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Job flow through the system

JOB

PURGEQUEUEHARD-COPYQUEUEOUTPUTQUEUEEXECUTIONQUEUECONVERSIONQUEUE


SYSOUTSYSIN

SYSOUT

JCL

JCL & SYSIN

(NJE)

SPOOLSPOOL

DISKDISK



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JES2 compared to JES3

n a mu t -processor con gurat on:

JES2:

job output processing.

It is possible to configure JES2 to share spool and checkpoint data sets- .

JES3: Centralized control over processing through a single global JES3

processor, w c oes o se ec on, sc e u ng, an ev ce a oca onthe other JES3 systems.

The centralized control of JES3 provides increased job schedulingcontrol, deadline scheduling capabilities, and increased control byproviding its own device allocation.

Most installations use JES2, as do the examples in this text.



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What is workload manager?

Workload manager (WLM):

The component of z/OS that manages the processing of

goals, such as response time.

Also manages the use of system resources, such as processorsan storage, to accomp s t ese goa s.



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Summary

atc process ng s a un amenta unct on o z .

z/OS shares with JES the management of jobs and resources.

,processing, and controls their output.

JES manages jobs in queues.

An initiator sets up the necessary environment for running abatch job. Multiple initiators permit the parallel execution ofbatch obs.

During the life of a job, both JES and the z/OS base controlprogram control different phases of the overall processing.


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