Performing a write operation on the target generates one of the following actions, depending  on the bitmap: GLYPH<SM590000> 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. GLYPH<SM590000> If the bitmap indicates the grain to be modified on the target was copied, it is directly  changed. The bitmap is  not updated, and the grain is modified on the target with the new  value, as shown in Figure 11-8. Note:  If the entire grain is to be modified and not only part of it (some blocks only), the  copy on demand is bypassed. The bitmap is updated, and the grain on the target is  modified but not copied first. Figure 11-8 Modifying an already copied grain on the Target Figure 11-7 Modifying a non-copied grain on the target Chapter 11. Advanced Copy Services  445