text: Performing a write operation on the target generates one of the following actions, depending 
  on the bitmap: 
  
  (cid:2) If the bitmap indicates the grain to be modified on the target is not yet copied, it is first 
  copied from the source (copy on demand). The bitmap is updated, and the grain is 
  modified on the target with the new value, as shown in Figure 11-7. The source volume 
  remains unchanged. 