Hitachi Virtual Storage Platform, User And Reference Manual

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Functional and Operational Characteristics
2–41
Hitachi VSP User and Reference Guide
784
2 of 2 TrueCopy
TrueCopy for
Mainframe Notes: (continued)
6. If an MP to which the path between DKCs belongs
is overloaded, switching to an alternate path delays
and host MIH or time-out may occur.
7. If an RI/O retry occurs due to other factors than
RI/O MIH (5 sec), such as a check condition report
issued from RCU to MCU, the RI/O retry is
performed on the same path instead of an alternate
path. If a response delay to the RI/O occurs
constantly on this path due to path failure or link
delay, host MIH or time-out may occur due to
response time accumulation for each RI/O retried
within 5 seconds.
8. Even though the mode is set to ON, if
Mainframe host MIH time or Open host time-out
time is set to 10 seconds or less, host MIH or time-
out may occur due to a path failure between DKCs.
9. Operation commands are not available for
promptly switching to an alternate path.
10. The mode works for the pair for which initial
pair creation or Resync operation is executed.
11. Micro-program downgrade to an unsupported
version cannot be executed unless all the TC Sync
for z/OS or TC Sync pairs are suspended or deleted.
12. See the appendix of the SOM for operational
specifications in each combination of MCU and RCU.
OFF MCU/RCU
787 Compatible
FlashCopy(R)
V2 This mode enables the batch prefetch copy.
Mode 787 = ON:
The batch prefetch copy is executed for an FCv2
pair and a Preserve Mirror pair
Mode 787 = OFF (default):
The batch prefetch copy is not executed.
Notes:
1. When the mode is set to ON, the performance
characteristic regarding sequential I/Os to the
FCv2target VOL changes.
2. The mode is applied only when SOM 577 is set
to OFF
3. The mode is applied if response performance for
a host I/O issued to the FCv2 target VOL is
prioritized
OFF ..
Mode Category Description Default MCU/RCU