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Chapter 2 Data Replication
16
2
2
2
.
.
.
3
3
3
.
.
.
4
4
4
A
A
A
c
c
c
t
t
t
i
i
i
v
v
v
i
i
i
t
t
t
y
y
y
S
S
S
t
t
t
a
a
a
t
t
t
e
e
e
a
a
a
n
n
n
d
d
d
S
S
S
y
y
y
n
n
n
c
c
c
h
h
h
r
r
r
o
o
o
n
n
n
o
o
o
u
u
u
s
s
s
S
S
S
t
t
t
a
a
a
t
t
t
e
e
e
In data replication, Replicate, Restore, and Separate states are called “activity states”, or simply
“activities”.
The execution states indicating state transitions and the state in which the state transition is complete
are called “synchronous states”.
Table 2-1 shows the activity states and synchronous states which transit as a result of each replication
operation. For information on handling MV and RV access in the activity states, refer to 2.6 “RV
Access Restriction”.
Table 2-1 Activity State and Synchronous State
Activity State Synchronous State Description
Separate Execution
(sep/exec)
• Temporal state until the difference between MV and RV
becomes zero after Separate
• As a rule, read and write to RV are not allowed.
Separated(separated)
• Data copy between MV and RV is not performed. This
state occurs immediately after the pair setting.
• Normally, read and write to RV are allowed.
Forced Separate(cancel)
• MV and RV are forcibly separated by Forced Separate.
• Read and write to RV are allowed.
Separate State
Failure Separation (fault)
• MV and RV are forcibly separated in the disk array due
to a copy fault.
• Read and write to RV are allowed.
Synchronous Execution
(rpl/exec)
• Reflection of the difference between MV and RV at
Replicate has not been completed (The difference is
being reflected from MV to RV).
• Updates to MV is reflected to RV.
• As a rule, read and write to RV are not allowed.
Replicate State
Synchronous State(rpl/sync)
• Reflection of the difference between MV and RV at
Replicate has been completed.
• Updates to MV is reflected to RV.
• As a rule, read and write to RV are not allowed.
Restore Execution(rst/exec)
• Reflection of the difference between MV and RV at
Restore has not been completed (The difference is being
reflected from RV to MV).
• When Restore(update) is executed, the updated data of
the MV is reflected into the RV.
• When Restore(protect) is executed, the updated data of
the MV is not reflected into the RV.
• As a rule, read and write to RV are not allowed.
Restore State
Synchronous State(rst/sync)
• Reflection of the difference between MV and RV at
Restore has been completed.
• When Restore(update) is executed, the updated data of
the MV is reflected into the RV.
• When Restore(protect) is executed, the updated data of
the MV is not reflected into the RV and the Separate
completion state is automatically entered.
• As a rule, read and write to RV are not allowed.