text: **3.15.1 FlashCopy guidelines**
  
  When planning to use FlashCopy, observe the following guidelines: 
  
  (cid:2) Identify each application that must have a FlashCopy function implemented for its volume. 
  
  (cid:2) Identify storage pool or pools that will be used by FlashCopy volumes. 
  
  (cid:2) Define which volumes need to use FlashCopy 
  
  (cid:2) For each volume, define which FlashCopy type best fits your requirements: 
  
  – No copy 
  – Full copy 
  – Thin-Provisioned 
  – Incremental 
  
  (cid:2) Define how many copies you need and the lifetime of each copy. 
  
  (cid:2) Estimate the expected data change rate for FlashCopy types other than full copy. 
  
  (cid:2) Consider memory allocation for copy services. If you plan to define multiple FlashCopy 
  
  relationships, you might need to modify the default memory setting. For more information, 
  see 11.2.18, “Memory allocation for FlashCopy” on page 496. 
  
  (cid:2) Define the grain size that you want to use. When data is copied between volumes, it is 
  
  copied in units of address space known as*grains*. The grain size is 64 KB or 256 KB. The 
  FlashCopy bitmap contains 1 bit for each grain. The bit records whether the associated 
  grain was split by copying the grain from the source to the target. Larger grain sizes can 
  cause a longer FlashCopy time and a higher space usage in the FlashCopy target volume. 
  The data structure and the source data location can modify those effects. 