HP StorageWorks XP Remote Web Console Software User Manual
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Chapter 3 Preparing for Universal Replicator z/OS Operations
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Hitachi Universal Replicator for IBM /OS User’s Guide
Planning Data Transfer Speed before Reversing Data Volumes
When a failure occurs at a host, one of the failure recovery measures is to
reverse the primary data volume and the secondary data volume (i.e., change
the copy direction). If you want to reverse the primary data volume and the
secondary data volume, usually you must ensure that the data transfer speed
is the same before and after you reverse these data volumes. Therefore, when
you do planning on master journal volumes and restore journal volumes, you
need to apply the same scheme to both master and restore journal volumes.
If you do not want to reverse the primary data volume and the secondary data
volume, you will be able to cope with a temporary increase in data transfers
and a communication path failure between the primary storage system and
the secondary storage system, if the master journal volume satisfies
conditions mentioned earlier. Therefore, the data transfer speed and the
volume capacity required for restore journal volumes are smaller than those
required for master journal volumes. Note that the data transfer speed for
journal volumes must exceed the data transfer speed in "normal status".
Contributing Factors for Data Transfer Speed between
Storage Systems
The speed of data transfer between the primary storage system and the
secondary storage system depends on the following factors:
•
The bandwidth of data transfer paths
•
The journal transfer speed of the DKC
The data transfer speed between the primary storage system and the
secondary storage system must exceed the data transfer speed in "normal
status" mentioned in Figure 3-33 below. If a temporary increase in transferred
data occurs and the data transfer speed between the primary storage system
and the secondary storage system is exceeded, the excess data will be stored
temporarily in journal volumes.