When a write operation is requested to an area of the source volume that Compatible FlashCopy® V2 has not yet copied to the target volume, a copy of the point-in-time (pre-update) data is first written to the target volume. Then, the update is written to the source volume. This process is called on-demand copy. On-demand copy works in both COPY mode and NOCOPY mode.
CAUTION:
When you select NOCOPY mode, even if all data in the S-VOL is copied to the T-VOL through on-demand copy,
Compatible FlashCopy® V2 does not automatically withdraw the relationship. Therefore, when you select NOCOPY mode, you must withdraw the relationship explicitly using the
FCWITHDR command.
If you select the NOCOPY2COPY mode (Compatible FlashCopy® V2 only) for a relationship created using NOCOPY mode, the background copy operation is performed. When all data is copied, the relationship is automatically released.