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Oracle Performance Tuning and Optimization
(Publisher: Macmillan Computer Publishing)
Author(s): Edward Whalen
ISBN: 067230886x
Publication Date: 04/01/96

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Chapter 17
Batch Processing System

Batch processing systems are different from OLTP systems in that batch jobs are not run interactively. Batch jobs are submitted at some later time (perhaps much later) and run until they are done. The batch processing system typically contains many of the attributes of both the OLTP system and the decision support system, with some additional unique attributes. It is difficult to characterize a batch processing system accurately because the types of jobs run in batch tend to vary quite a lot.

To generalize, batch processing usually involves loading and unloading large amounts of data on the system, creating indexes, detail reporting, and so on. Batch processing often occurs when no other work is being done on the system.

The types of work typically done in batch may include, but are not limited to, some of the following activities:

  Summary and detailed reports
  End-of-month, end-of-quarter, and end-of-year books
  Database imports/exports
  Payroll processing
  Database merges

These are just a few of the types of activities typically run in batch. The following section looks at some of the characteristics of batch processing.

Characteristics of the Batch Processing System

Although there is no such thing as a “typical” batch processing system, there are some characteristics of batch processing. A batch processing system usually has some of the following characteristics:

  The data to be processed on the system is loaded just before processing. In fact, the loading of the data is considered part of the batch processing job.
  Index creation. The data is often indexed immediately after loading and before processing.
  The types of processing varies. Processing can consist of joins, sorts, and so on; anything is possible based on the processing job.
  Queries are much more complex in a batch processing job than they are in OLTP jobs.
  Generates intense activity on the part of the server components. Most components of the system run at 100 percent for the duration of the job.

The load on the batch processing system is very high for a certain length of time. In fact, because response times are not an issue for batch processing, it is reasonable to push the system to its limits. Rather than spreading out the load and trying to achieve reasonable response times (as you do in an OLTP system), the goal of the batch processing system is to push the system to its limits to get the work done in as short an amount of time as possible.

It is not uncommon for batch processing systems to have fairly strict windows in which to do their job. It is therefore essential that the system run at 100 percent until that job is completed.

The batch processing system has several unique characteristics:

  Batch processing systems are typically dedicated to the job at hand. No other processing occurs on the system.
  Database loads and unloads are typically part of batch processing.
  Index creation is typically part of the batch processing job.

These characteristics are unique to batch processing systems and can tell us quite a bit about the data access patterns we should expect to see in this type of system.

Data Access Patterns

Because of the unique characteristics of the batch processing system, you will probably see the following data access patterns on this type of system:

  Heavy I/O usage. Batch processing systems usually generate large amounts of I/O to the data files. During load and unload, this activity is sequential. The type of I/O during the query processing depends on the type of processing being done.
  Heavy sequential I/O to load/unload files. The data being loaded creates heavy sequential I/O, as does the unloading of the results.
  Heavy index file access. During index creation, the indexes are used very heavily.
  Moderate to heavy redo log usage. The amount of access to the redo log depends on the type of processing being done.
  Moderate to heavy use of rollback segments. The amount of access to the rollback segments also depends on the type of processing.
  Large amounts of memory are used. The memory is used not only for the SGA but for sorting and so on.

You can use these characteristics to help design and tune the batch processing system for optimal performance. The first step in this design process is to set goals for what you want to achieve.


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