An overview about Batch Systems:

An overview about Batch Systems:

A major part of the workload on mainframe computers consists of batch processing. A large mainframe often will run several thousand batch jobs every day. This “network” of jobs represents a business workflow with complex interrelations requiring careful scheduling and prioritizing to ensure that all batch jobs run in the correct order and meet strict deadlines. Consequently, sophisticated systems have evolved to manage and run batch workloads— systems that “feel” mainframe-specific, with no obvious parallels in Windows®-based computing. Approached with the idea of migrating batch applications to the Windows operating system, most IT managers react with, “How can that be possible?” From another angle, many other people assume modern applications no longer require batch processing— an opinion that is completely wrong. The Windows operating system is quite capable of supporting the complex needs of batch applications as has been demonstrated by the many organizations that have migrated batch systems to the Windows platform. The continuing need for batch processing is illustrated by key Microsoft® products, such as BizTalk® Server, which support workflows very similar to those of mainframe batch systems.

Overview

Batch systems are collections of programs that run without interaction with users and with minimal interaction with a computer operator, where “minimal” means no more than the computer operator setting parameters at the start of a batch job and changing tapes or other data storage devices when prompted. Many of today’s batch systems automate these tasks so there is no interaction with humans unless something goes wrong. Most mature mainframe systems rely on batch jobs to perform significant portions of the total application logic. The types of tasks undertaken include:

• Merging the day’s transactions into master files

• Sorting data files for optimal processing the following day

• Merging data from multiple locations

• Providing daily, weekly, monthly, and annual reports

• Issuing daily, weekly, and monthly bills or invoices to customers

• Performing daily, weekly, biweekly, and monthly payroll calculations

• Consolidating multiple orders into single shipments and invoices

• Printing checks

• Performing special mailings

• Applying interest to financial accounts

• Batching orders for transmission to another company

• Performing backups

• Archiving data

• Auditing transactions and systems

Some companies may be able to survive for a day or two without running batch systems, but

most will find business operations degrading rapidly if the batch applications are not run.



Batch Components

The main components of the IBM mainframe batch ecosystem are:

• Job entry subsystem (JES)—queues and assigns jobs to initiators

• Initiator—responsible for running a job

• Job—one or more executable programs

• JCL—describes the job, including file name cross-references, executable commands, and

control flow, and provides control parameters to the JES

• Scheduler—schedules job start times, codifies dependencies between jobs and their runtime

requirements, and provides reporting and alerting capabilities

• Data files and databases