38 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
This function is called Global Mirror cycling mode. Figure 2-15 shows an example of this 
function where you can see the relationship between volumes and change volumes.
Figure 2-15   Global Mirror with change volumes
In asynchronous remote copy, the application acknowledges that the write is complete before 
the write is committed at the secondary volume. Therefore, on a failover, certain updates 
(data) might be missing at the secondary volume. The application must have an external 
mechanism for recovering the missing updates, if possible. This mechanism can involve user 
intervention. Recovery on the secondary site involves starting the application on this recent 
backup, and then rolling forward or backward to the most recent commit point.
2.5.26  FlashCopy and Transparent Cloud Tiering
FlashCopy and Cloud Backup are used to make a copy of a source volume on a target 
volume. After the copy operation starts, the original content of the target volume is lost. The 
target volume has the contents of the source volume as they existed at a single point in time. 
Although the copy operation takes time, the resulting data at the target appears as though the 
copy was made instantaneously.
FlashCopy
FlashCopy is sometimes described as an instance of a time-zero (T0) copy or a point-in-time 
(PiT) copy technology.
FlashCopy can be performed on multiple source and target volumes. FlashCopy permits the 
management operations to be coordinated so that a common single point in time is chosen 
for copying target volumes from their respective source volumes. 
With IBM Spectrum Virtualize, multiple target volumes can undergo FlashCopy from the same 
source volume. This capability can be used to create images from separate points in time for 
the source volume, and to create multiple images from a source volume at a common point in 
time. Source and target volumes can be thin-provisioned volumes.
Reverse FlashCopy enables target volumes to become restore points for the source volume 
without breaking the FlashCopy relationship, and without waiting for the original copy 
operation to complete. IBM Spectrum Virtualize supports multiple targets and therefore, 
multiple rollback points.
Most clients aim to integrate the FlashCopy feature for point-in-time copies and quick 
recovery of their applications and databases. An IBM solution to this configuration is provided 
by IBM Spectrum Protect™, which is available at this website.