IBM System storage DS6000 Series Redbook page 70
Copy services with ibm system z
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Also See for System storage DS6000 Series:
- Redbooks (406 pages) ,
- Attachment manual (298 pages) ,
- Introduction and planning manual (119 pages)
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While the FlashCopy relationship is being created, the DS6000 holds off the I/O activity to
the volume for an interval of time by putting the source volume in an
condition. No user intervention is required. I/O activity resumes when the FlashCopy
establish
If all bits for the bitmap representing the target are set to their initial values, this means
that no data block has been copied so far. The data in the target is not modified during
setup of the bitmaps. At this very first step the bitmap and the data look as illustrated in
Figure 6-2.
FlashCopy established at time t0 (time-zero)
t
0
t
0
Figure 6-2 FlashCopy at time t0
Once the relationship has been established, it is possible to perform read and write I/Os
on both the source and the target. Assuming that the target is used for reads only while
production is ongoing, things will look as illustrated in Figure 6-3.
Writing to the source and
reading from the source and the target
t
0
read
t
Figure 6-3 Reads from source and target volume and writes to source volume
46
IBM System Storage DS6000 Series: Copy Services with IBM System z
process is completed.
source
data
t
t
t
t
t
0
0
0
0
0
t
t
t
x
y
z
write x
write y
write z
source
data
t
t
t
t
t
0
x
0
z
0
before physical write to the source:
copy time-zero data from the source to the target
1
1
1
1
target
read 1
time-zero data not yet
available in the target:
read it from the source.
1
0
t
0
0
extended long busy
time
bitmap
1
1
data
time
read 2
bitmap
1
0
1
1
target
data
t
0
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