
Chapter 18. Copy Services performance 611
Figure 18-12 Application write I/O within two consistency group points
Figure 18-12 summarizes roughly what happens when NVS in the remote storage server is
overcommitted. A read (3) and a write (4) to preserve the source track and write it to the C
volume are required before the write (5) can complete. Eventually, the track gets updated on
the B1 volume to complete the write (5). But usually, all writes are quick writes to cache and
persistent memory and happen in the order as outlined in Figure 18-10 on page 608.
You can obtain a more detailed explanation of this processing in DS8000 Copy Services f ...