438 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
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.
FlashCopy mappings between multiple volumes can be grouped in a Consistency group to 
ensure that their T0 is identical for all of them. A simple one-to-one FlashCopy mapping does 
not need to belong to a consistency group.
Figure 11-1 shows the basic terms that are used with FlashCopy. All elements are explained 
in this chapter.
Figure 11-1   FlashCopy terminology
11.1.3  FlashCopy Mapping
The relationship between the source volume and the target volume is defined by a FlashCopy 
mapping. The FlashCopy mapping can have three different types, four attributes, and seven 
different states.
The FlashCopy mapping can be one of the following types:
/SM590000Snapshot: Sometimes referred to as nocopy. A T0 copy of a volume without a background 
copy of the data from the source volume to the target. Only the changed blocks on the 
source volume are copied. The target copy cannot be used without an active link to the 
source.