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the entire SAP system. With workload management, System z can run at high utilization rates
(up to 100%) and offers the unique option of accelerating or delaying transactions in an SAP
system selectively, depending on business needs.
The exception is when the middleware of the workload is instrumented with automatic restart
manager (ARM). In such a configuration, the middleware can move the correlator to the z/OS
and workload manager for System z can recognize the presence of the correlator and
perform the classification by using the correlator as a filter.
2.3 Business continuity
2.3.1 High availability
Business continuity has the following aspects:
► High availability (avoidance of unplanned outages)
► Continuous operation (avoidance or reduction of panned outages)
► Continuous availability (disaster recovery)
The following sections define the terms that are used to indicate the degrees of availability of the
various components of an SAP installation. For information about SAP software that supports
business continuity, see “Software considerations for business continuity” on page 166.
High availability is the capability to reduce the impact of unplanned outages by eliminating
SPOFs and thus is a measure of reliability. High availability is gained through server and
subsystem redundancies and tight integration with server failover. If any server fails as a
result of the hardware, the software, or a user, the users can continue their work because the
applications continue to run on an available server.
2.3.2 Continuous operation
Continuous operation refers to the ability to avoid planned outages, which means that system
outages for maintenance must be organized in a nondisruptive manner. Applications must
remain available to their users. To avoid planned outages, server and subsystem
redundancies are also used.
Because unplanned outages can still occur, a system running in continuous operation mode
does not necessarily qualify as being highly available.
2.3.3 Continuous availability
Continuous availability combines the characteristics of high availability and continuous
operation, so that it can reduce the impact of planned and unplanned outages. The goal is to
keep the systems running as close to 24 hours a day, 365 days a year, as possible.
Continuous availability is what most customers want to achieve. To provide it, a
continuous-availability setup needs to use necessary redundancy, cluster technology,
automation, mirroring, and online backup.
IBM System z is designed for zero downtime (planned and unplanned) and provides
end-to-end availability of applications and their underlying hardware. The combination of DB2
and z/OS provides a reliable infrastructure for strong business applications, offers superior
resilience and disaster recovery mechanisms, and allows online maintenance. Because
SPOFs are eliminated, the risks and costs of outages are minimized.
Chapter 2. Architectural overview of SAP NetWeaver with DB2 for z/OS 17