IBM DS8000 User Manual page 153

each consistency group. The default is zero seconds, which means that
Global Mirror will continuously form consistency groups as fast as the
environment will allow.
In most situations, it is recommended that you leave the default value of
zero to allow Global Mirror to form consistency groups as fast as possible.
Global Mirror automatically moves to Global Copy mode for a period of
time if the drain time is exceeded.
Maximum consistency group drain time
The maximum amount of time that Global Mirror spends draining data
from the A and B volumes in a consistency group. If this process is not
done during this time, a consistency group failure is reported. If the
maximum drain time is exceeded, then Global Mirror will transition to
Global Copy mode for a period of time in order to catch up in the most
efficient manner.
The default maximum drain time value is 30 seconds. Setting a maximum
drain time protects production performance by not permitting consistency
groups to form at times when it might not be desirable. It is recommended
that you not change the default of this setting.
Maximum coordination interval
The maximum time that Global Mirror will allow for the formation of the
consistency group before failing this consistency group. Having this time
value set ensures that if there is an error recovery event or communications
problem, applications will not experience significant impact from
consistency group formation failure. The default is 50 ms. It is
recommended that you not change the default of this setting.
Automated disaster recovery offerings for Metro/Global Mirror
The Metro/Global Mirror function has a number of supported automated
management offerings for disaster recovery solutions.
IBM offers a portfolio of automated solutions that are available to help you
implement a disaster recovery plan that best fits your IT environment. These
solutions require some sort of automation that can react to a failure in a timely
manner. Automated solutions, such as GDPS with Global Mirror, can monitor and
manage data resources during planned and unplanned outages.
GDPS is an automated disaster recovery solution for System z environments. In a
GDPS environment, a combination of Remote Mirror and Copy and Global Mirror,
™
or HyperSwap Manager and Global Mirror, manages the mirroring of data (both
disk and tape) between your local and remote sites. Data consistency is provided
across all platforms that share the storage units in a GDPS configuration.
When you combine the Global Mirror and Metro Mirror technologies with
automation, you can ensure continuous or near-continuous availability during
outages, including disasters. With automation, synchronization is achieved through
the point in time of the freeze by issuing commands in parallel to all logical
subsystems (LSSs) that are contained within the Metro Mirror consistency group
configuration. This ensures consistent data across all LSSs in the secondary copy of
data during a disaster.
With GDPS, you can write scripts or even a single GDPS script to perform tasks
that allow operations to be run in parallel across systems. The amount of work is
spread evenly across the defined tasks in parallel. GDPS can consolidate and check
the results and subsequently provide feedback on the status of the operations.
Chapter 8. Optional feature codes for the DS8000
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