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3-58 Chapter 3 Preparing for Universal Replicator z/OS Operations
Hitachi Universal Replicator for IBM /OS User’s Guide
Data transfer speed
between hosts and
the MCU
Data transfer speed of journal volumes
Data transfer speed
between the MCU and the RCU
Time
Normal status
Temporary increase in
data to be transferred
Data transfer
speed
Figure 3-32 Data Transfer Speed with URz (Influence on Journal Volume
Capacity)
The following factors determine the required journal volume capacity:
• the period of time during which data transfer can continue between hosts
and the primary storage system when a temporary increase in transferred
data occurs or when a communication path failure occurs between the
primary and secondary storage system.
• the data transfer speed for the period of time that is mentioned above
To determine the journal volume capacity, use the following formula. In this
formula, V
H-M
is the data transfer speed between hosts and the primary
storage system. V
M-R
is the data transfer speed between the primary storage
system and the secondary storage system. t is the length of time during which
data transfer can continue.
Journal volume capacity > V
H-M
- V
M-R
× t
If you want to calculate journal volume capacity that is required when a
communication path failure occurs between the primary storage system and
the secondary storage system, please assign 0 (zero) to V
M-R
.
The total capacity of journal volumes in each journal group must exceed the
value illustrated above.