text: You can create a FlashCopy of your source and use that for your testing. This copy is a 
  duplicate of your production data down to the block level so that even physical disk identifiers 
  are copied. Therefore, it is impossible for your applications to tell the difference. 
  
  You can also use the FlashCopy feature to create restart points for long running batch jobs. 
  This option means that if a batch job fails several days into its run, it might be possible to 
  restart the job from a saved copy of its data rather than rerunning the entire multiday job. 
  
  **11.1.2 FlashCopy principles and terminology**
  
  The FlashCopy function creates a point-in-time or time-zero (T0) copy of data that is stored 
  on a*source volume*to a*target volume*by using a*copy on write*and*copy on-demand*
  mechanism. 
  
  When a FlashCopy operation starts, a checkpoint creates a*bitmap table*that indicates that 
  no part of the source volume was copied. Each bit in the bitmap table represents one region 
  of the source volume and its corresponding region on the target volume. Each region is called 
  a*grain*. 
  
  The relationship between two volumes defines the way data are copied and is called a 
  *FlashCopy mapping*. 