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 Description Advantages Considerations
Metro/Global Mirror Three-site, long
distance disaster
recovery replication
A backup site is
maintained
regardless of which
one of the sites is
lost.
Recovery point
objective (RPO)
might grow if
bandwidth capability
is exceeded.
Metro Mirror Synchronous data
copy at a distance
No data loss, rapid
recovery time for
distances up to 300
km.
Slight performance
impact.
Global Copy Continuous copy
without data
consistency
Nearly unlimited
distance, suitable for
data migration, only
limited by network
and channel
extenders
capabilities.
Copy is normally
fuzzy but can be
made consistent
through
synchronization.
Chapter 1. Introduction to IBM System Storage DS8000 series 29
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