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## Target writes with Multiple Target FlashCopy 

A write to an intermediate or newest target volume must consider the state of the grain within its own mapping, and the state of the grain of the next oldest mapping: 

GLYPH<SM590000> If the grain of the next oldest mapping has not been copied yet, it must be copied before the write is allowed to proceed to preserve the contents of the next oldest mapping. The data that is written to the next oldest mapping comes from a target or source. 

GLYPH<SM590000> If the grain in the target being written has not yet been copied, the grain is copied from the oldest already copied grain in the mappings that are newer than the target, or the source if none are already copied. After this copy is done, the write can be applied to the target. 

## Target reads with Multiple Target FlashCopy 

If the grain being read has already been copied from the source to the target, the read simply returns data from the target being read. If the grain has not been copied, each of the newer mappings is examined in turn and the read is performed from the first copy found. If none are found, the read is performed from the source. 

## 5.2.4 FlashCopy planning considerations 

The FlashCopy function, like all the advanced IBM Spectrum Virtualize and Storwize family product features, offers useful capabilities. However, some basic planning considerations are to be followed for a successful implementation. 

## FlashCopy configurations limits 

To plan for and implement FlashCopy, you must check the configuration limits and adhere to them. Table 5-3 shows the system limits that apply to the latest version at the time of writing this book. 

<img src='content_image/1012844.jpg'>

Configuration Limits:  The configuration limits always change with the introduction of new hardware and software capabilities. Check the IBM Spectrum Virtualize/Storwize online documentation for the latest configuration limits. 

