## FlashCopy 

FlashCopy refers to a point-in-time copy where a virtual copy of a volume is created. The target volume maintains the contents of the volume at the point in time when the copy was established. Any subsequent write operations to the source volume are not reflected on the target volume. 

## FlashCopy mapping 

A FlashCopy mapping is a continuous space on a direct-access storage volume that is occupied by or reserved for a particular data set, data space, or file. 

## FlashCopy relationship 

See FlashCopy mapping. 

## FlashCopy service 

FlashCopy service is a copy service that duplicates the contents of a source volume on a target volume. In the process, the original contents of the target volume are lost. See also “Point-in-time copy” on page 808. 

## Flash drive 

A data storage device that uses solid-state memory to store persistent data. 

## Flash module 

A modular hardware unit that contains flash memory, one or more flash controllers, and associated electronics. 

## Front end and back end 

The SVC takes MDisks to create pools of capacity from which volumes are created and presented to application servers (hosts). The volumes that are presented to the hosts are in the front end of the SVC. 

## Global Mirror 

Global Mirror (GM) is a method of asynchronous replication that maintains data consistency across multiple volumes within or across multiple systems. Global Mirror is generally used where distances between the source site and target site cause increased latency beyond what the application can accept. 

## Global Mirror with change volumes 

Change volumes are used to record changes to the primary and secondary volumes of a remote copy relationship. A FlashCopy mapping exists between a primary and its change volume, and a secondary and its change volume. 

## Grain 

A grain is the unit of data that is represented by a single bit in a FlashCopy bitmap (64 KiB or 256 KiB) in the SVC. A grain is also the unit to extend the real size of a thin-provisioned volume (32 KiB, 64 KiB, 128 KiB, or 256 KiB). 

## Hop 

One segment of a transmission path between adjacent nodes in a routed network. 

