HP StorageWorks XP Remote Web Console Software - Manual (Page 95)

Hitachi TrueCopy for z/OS user guide 95
If you select Disable, the MCU will reject the CGROUP command. Enable the FREEZE option only after all
MCU-RCU paths have been added.
The Round Trip Time setting is used for Initial Copy operations. This setting gives a priority to a remote I/O
for an update copy operation.
When an Initial Copy operation is in progress, the copy pace is automatically adjusted based on the value
(the actual time required for the initial copy), which can be obtained by subtracting the specified Round
Trip time (obtained using the formula below) from the remote I/O response time. When the actual time
required for the initial copy operation is large, it means that the workload of the update copy is relatively
high. Therefore, the copy pace of the initial copy will be slowed. When the time is relatively small, the
copy pace will speed up to the specified value. In this way, we can curb the influence of the exclusive line
use in the initial copy operation on the host performance.
NOTE: This option is available only in the case of TCz pairs (In the case of TCzA pairs, this option value
is invalid).
The default value of Round Trip Time is 1 ms. You may specify 1 ms to 500 ms. You can use the following
formula to figure out the Round Trip Time.
For Round Trip Time between MCU and RCU, please ask your carrier, or use a ping command and etc. to
measure the time. If you do not use lines etc. between MCU and RCU, specify “1.”
Initial Copy response time is the response time required for multiple initial copy operations. You can use
the following formula to get the Initial Copy response time. To get the time, you should use the following
Round Trip time = Round Trip Time between MCU-RCU x 2
1
+ Initial Copy response time (ms)
1. A data transfer between MCU and RCU involves two response sequences in one command issuance. Therefore, you need to
double the Round Trip Time between MCU-RCU.