The FlashCopy function creates a point-in-time copy of data that is stored on a source volume to a target volume.
In its basic mode, the FlashCopy function creates copies of content on a source volume to a target volume in a mapping. The function associates a source volume and a target volume in a mapping. If data exists on the target volume, that data is replaced by the copied data.After the copy operation has completed, the target volumes contain the contents of the source volumes as they existed at a single point in time, unless target writes have been processed. FlashCopy is sometimes described as an instance of a time-zero copy (T 0) or point-in-time copy technology. Although the copy operation takes some time to complete, the resulting data on the target volume is presented so that the copy appears to have occurred immediately, and all data is available immediately. (If needed, data that is still in the process of being copied can be accessed from the source.)
The system can support up to 2048 volumes, but the maximum number of target volumes for the system is 64.
Although it is difficult to make a consistent copy of a data set that is constantly updated, point-in-time copy techniques help solve this problem. If a copy of a data set is created using a technology that does not provide point-in-time techniques and the data set changes during the copy operation, the resulting copy might contain data that is not consistent. For example, if a reference to an object is copied earlier than the object itself and the object is moved before it is copied, the copy contains the referenced object at its new location, but the copied reference still points to the previous location. You can also assign background copy and cleaning rates to a FlashCopy mapping to control the rate at which updates are propagated to the remote system. FlashCopy mapping copy rate values can be from 128 KBps to 2 GBps and can be changed when the FlashCopy mapping is in any state.
More advanced functions allow operations to occur on multiple source and target volumes. Management operations are coordinated to provide a common, single point-in-time for copying target volumes from their respective source volumes. This creates a consistent copy of data that spans multiple volumes. The function also supports multiple target volumes to be copied from each source volume. This can be used to create images from different points in time for each source volume.