Application System/400

Mid-range Machine

Features

• 64 bit RISC processor low cost mid-range machine.

• 64 bit memory addressing.• Certified “C2” level most

secured system.• DBCS supports more than 50

world languages.• RDBMS integrated with OS/400.• Multi-user , multitasking

OS/400.

More Features

• Object based system. • Net work by TCP/IP, SNA and

IPX.• New iseries supports web

technologies, fax, email.• LPAR – allows multiple

instances of OS/400.

Software on AS/400

• OS/400 V5R1.• DB2/400 RDBMS.• Language Compilers RPG IV,

COBOL/400, C/400, C++/400 , BASIC, PASCAL, CL/400.

• SQL/400.• Query/400.• Query Manager.

Storage on AS/400

• Single Level storage combines RAM and DASD into logical units.

• Auxiliary Storage Pool (ASP) is logical grouping of disk units.

• Everything that is stored on AS/400 as a separate entity is an Object.

• There are around 100 types of Objects.

• Library: Object to which other objects belong Logically.

Storage Hierarchy

QSYSSystem Library

All libraries belong to this

QSYSSystem Library

All libraries belong to this

QGPL QRPG QTEMP QCBL Infy Satish

RPG compiler Objects COBOL Compiler ObjectsProgram/Database

Objects createdby Satish

All Objects belong to any library.

iSeries Work management

•Subsystem•Queues•Memory Pools•Jobs

Subsystem

• Subsystem is a module of operating system dedicated to execute particular type/class of jobs.

• It’s a execution environment for the grouped jobs who may share resources.

• system can contain several subsystems, all operating independently of each other. Subsystems manage resources. Each subsystem can run unique operations.

Controlling subsystem

• The controlling subsystem is the interactive subsystem that starts automatically when the system starts, and it is the subsystem through which the system operator controls the system during system startup.

Subsystems

• QBASE (controlling subsystem) Qbase supports interactive, batch, and communications jobs. It has an autostart job, which automatically starts the Qusrwrk, Qserver, and Qspl subsystems.QCTL

• QCMN• QSPL

Subsystem: Objectives

• Load Balancing– Multiple subsystems on one server run

concurrently to run their respective jobs.

• Isolation– Memory and object resources of

subsystems can be isolated form each other if so required.

• Security– User can submit jobs to a subsystem

only to which they have permissions.

Subsystem for better performance

• Subsystems are created to improve performance.

• A system pool/Storage pool is logical division of main memory reserved for processing a job or group of jobs by the OS. It is shared by multiple jobs within a subsystem.

Main storage

• Main storage is divided in two: machine pool and base pool.

• Base pool is the part of main storage that remains after allocating machine pool.

• Base pool is shared pool for all subsystems.

Other shared pool

• *INTERACT :

• *SPOOL

• *SHRPOOL1 to *SHRPOOL10

…

Commands

• Creating Subsystem CRTSBS

• Shared pool sizes are controlled by CHGSHRPOOLWRKSHRPOOLDSPSBSD …Display subsystem

description.

Jobs

• A Unit of work to which system resources are allocated for its execution is called as a job.

• A Job has at least one thread within.

Various types of jobsAutoStart jobs

• An autostart job starts automatically when the subsystem it is associated with starts. These jobs generally perform initialization work that is associated with a particular subsystem. Autostart jobs can also perform repetitive work or provide centralized service functions for other jobs in the same subsystem.

Add Auto Start Job Entry

• ADDAJE SBSD(subsystem-name) JOB(REMINDER) JOBD(DMLIB/DMRMDR)

Prestart communications job

• A prestart communications job is a communications batch job that starts running before a remote system sends a program start request.

• A prestart job starts before a work request is received, either when the subsystem starts or as a result of the Start Prestart Jobs (STRPJ) command.

Batch jobs

• Batch jobs run in the system background, freeing the user who submitted the job to do other work.

• Batch jobs are typically low priority jobs. Several batch jobs can be active at the same time.

Batch jobs

• The Submit Job (SBMJOB) command allows a job that is being run to submit another job to a job queue to be run later as a batch job.

Scheduled Job

• The AS/400 has an excellent job scheduler. It will submit any job at a pre-scheduled time.

• Use the command Work With Job Schedule Entries, WRKJOBSCDE.

• From the Job Schedule menu, hit F6 to add a job. Simply fill in the values to define when and how often the job runs.

• Add Job Schedule Entry (ADDJOBSCDE)

Job Description

• The job description allows you to create a set of job properties that are saved and available for multiple uses. The job description can be used as the source for some of the job properties that tell the system how to run a job.

•

Job Description

• Job Description object contains set of job related attributes that can be used by one or more jobs. The attributes are like.– JOBQ of job– OUTQ of job– Library list– Job Scheduling priority.

• Thus these are some of the parameters on the command of creating Job description.

Job DescriptionCommands

CRTJOBD JOBD(BATCH3) USER(*RQD)

JOBQ(NIGHTQ) JOBPTY(4) OUTPTY(4)

ACGCDE(NIGHTQ012345)RTGDTA(QCMDB) TEXT(’Batch #3

jobdescription for high pty night

work’)

Job Queues

• Job queues are work entry points for batch jobs to enter the system. They can be thought of as "waiting rooms" for a subsystem. A number of factors affect when the job is pulled off the job queue into the subsystem, such as the job priority on the job queue, the sequence number of the job queue, and the maximum active jobs. When all of these factors work together, the job will be pulled off the job queue to start running in the subsystem.

JOB Queue Object Type: *JOBQ

• A job queue contains entries for jobs submitted by using the following commands that are being processed by the system:Start Database Reader (STRDBRDR)Start Diskette Reader (STRDKTRDR)Start Printer Writer (STRPRTWTR)Start Diskette Writer (STRDSKWTR)Submit Job (SBMJOB)Submit Database Jobs (SBMDBJOB)Submit Diskette Jobs (SBMDKTJOB)Transfer Job (TFRJOB)

Creating a JOBQ

CRTJOBQ JOBQ(DEPTA) AUT(*EXCLUDE)

TEXT(’Special queue for Dept A jobs’)

This JOBQ needs to be added to any specific subsystem.

ADDJOBQE = add job queue Entry