Comparison Of Licensed Functions - IBM DS8000 User Manual

z/OS Global Mirror
In the event of workload peaks, which might temporarily overload the
bandwidth of the Global Mirror configuration, the enhanced z/OS Global
Mirror function initiates a Global Mirror suspension that preserves primary
site application performance. If you are installing new high-performance
z/OS Global Mirror primary storage subsystems, this function provides
improved capacity and application performance during heavy write
activity. This enhancement can also allow Global Mirror to be configured to
tolerate longer periods of communication loss with the primary storage
subsystems. This enables the Global Mirror to stay active despite transient
channel path recovery events. In addition, this enhancement can provide
fail-safe protection against application system impact related to unexpected
data mover system events.
The z/OS Global Mirror function is an optional function. To use it, you
must purchase the remote mirror for z/OS 2244/239x function
authorization feature.
z/OS Global Mirror Multiple Reader (enhanced readers)
z/OS Global Mirror Multiple Reader provides multiple Storage Device
Manager readers allowing improved throughput for remote mirroring
configurations in System z environments. z/OS Global Mirror Multiple
Reader helps maintain constant data consistency between mirrored sites
and promotes efficient recovery. This function is supported on the DS8000
series running in a System z environment with version 1.7 or later at no
additional charge.

Comparison of licensed functions

A key decision that you must make in planning for a disaster is deciding which
licensed functions to use to best suit your environment.
Table 2 provides a brief summary of the characteristics of the Copy Services
features that are available for the storage unit.
Table 2. Comparison of licensed functions
Licensed function
Metro/Global Mirror Three-site, long
Metro Mirror
Global Copy
Description Advantages
A backup site is
distance disaster maintained
recovery replication regardless of which
one of the sites is
lost.
Synchronous data No data loss, rapid
copy at a distance recovery time for
distances up to 300
km.
Continuous copy Nearly unlimited
without data distance, suitable for
consistency data migration, only
limited by network
and channel
extenders
capabilities.
Chapter 1. Introduction to IBM System Storage DS8000 series
Considerations
Recovery point
objective (RPO)
might grow if
bandwidth capability
is exceeded.
Slight performance
impact.
Copy is normally
fuzzy but can be
made consistent
through
synchronization.
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