Mainframe concepts
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Mainframes working after hours: Batch processing

Mainframe concepts

Batch applications are processed on the mainframe without user interaction. A batch job is submitted on the computer; the job reads and processes data in bulk— perhaps terabytes of data— and produces output, such as customer billing statements. An equivalent concept can be found in a UNIX® script file or a Windows® command file, but a z/OS® batch job might process millions of records.

While batch processing is possible on distributed systems, it is not as commonplace as it is on mainframes because distributed systems often lack:

  • Sufficient data storage
  • Available processor capacity, or cycles
  • Sysplex-wide management of system resources and job scheduling

Mainframe operating systems are typically equipped with sophisticated job scheduling software that allows data center staff to submit, manage, and track the execution and output of batch jobs.

Batch processes typically have the following characteristics:

  • Large amounts of input data are processed and stored (perhaps terabytes or more), large numbers of records are accessed, and a large volume of output is produced.
  • Immediate response time is usually not a requirement. However, batch jobs often must complete within a batch window, a period of less-intensive online activity, as prescribed by a service level agreement (SLA).
  • Information is generated about large numbers of users or data entities (for example, customer orders or a retailer's stock on hand).
  • A scheduled batch process can consist of the execution of hundreds or thousands of jobs in a pre-established sequence.

During batch processing, multiple types of work can be generated. Consolidated information such as profitability of investment funds, scheduled database backups, processing of daily orders, and updating of inventories are common examples.

In Figure 1, consider the following elements at work in the scheduled batch process:

Figure 1. Typical batch use
  1. At night, numerous batch jobs running programs and utilities are processed. These jobs consolidate the results of the online transactions that take place during the day.
  2. The batch jobs generate reports of business statistics.
  3. Backups of critical files and databases are made before and after the batch window.
  4. Reports with business statistics are sent to a specific area for analysis the next day.
  5. Reports with exceptions are sent to the branch offices.
  6. Monthly account balance reports are generated and sent to all bank customers.
  7. Reports with processing summaries are sent to the partner credit card company.
  8. A credit card transaction report is received from the partner company.
  9. In the production control department, the operations area is monitoring the messages on the system console and the execution of the jobs.
  10. Jobs and transactions are reading or updating the database (the same one that is used by online transactions) and many files are written to tape.

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