HP StorageWorks XP Remote Web Console Software - Manual (Page 32)

Figure 14 Version 2 Relationship Cannot be Created
Copy Modes
When you establish a relationship, Version 2 allows you to select COPY mode or NOCOPY mode.
When you select COPY mode, Version 2 copies all the data in the S-VOL to the T-VOL. This process
is called background copying. Version 2 automatically withdraws the pair when the background
copying is complete. Note that when you select NOCOPY mode, the background copying operation
will not be performed.
If there is a request for a write operation to the space in the S-VOL from which the data is not yet
copied or a request for a read/write operation to the space in the T-VOL to which the data is not
yet copied, Version 2 first copies the old data in the S-VOL to the T-VOL. This process is called
on-demand copying.
(page 33) shows the process of on-demand copying.
32 About Version 2 Operations