text: The background copy rate property determines the speed at which grains are copied as a 
  background operation, immediately after the FlashCopy mapping is started. That speed is 
  defined by the user when creating the FlashCopy mapping, and can be changed dynamically 
  for each individual mapping, whatever its state. Mapping copy rate values can be 0 - 150, with 
  the corresponding speeds that are listed in Table 11-1. 
  
  When the background copy function is not performed (copy rate = 0), the target volume 
  remains a valid copy of the source data only while the FlashCopy mapping remains in place. 