Most mainframe workloads fall into one of two categories: Batch processing or online transaction processing, which includes Web-based applications.

One key advantage of mainframe systems is their ability to process terabytes of data from high-speed storage devices and produce valuable output. For example, mainframe systems make it possible for banks and other financial institutions to perform end-of-quarter processing and produce reports that are necessary to customers (for example, quarterly stock statements or pension statements) or to the government (for example, financial results). With mainframe systems, retail stores can generate and consolidate nightly sales reports for review by regional sales managers. The applications that produce these statements are batch applications, which are illustrated at the top of Figure 1.

In contrast to batch processing, transaction processing occurs interactively with the end user. This interaction is outlined at the bottom of Figure 1. Typically, mainframes serve a vast number of transaction systems. These systems are often mission-critical applications that businesses depend on for their core functions. Transaction systems must be able to support an unpredictable number of concurrent users and transaction types. Most transactions are executed in short time periods— fractions of a second in some cases.

Figure 1. Typical mainframe workloads