The total amount of cache memory reserved for the FlashCopy bitmaps limits the amount of  capacity that can be used as a FlashCopy target. Table 6-4 illustrates the relationship of  bitmap space to FlashCopy address space, depending on the size of the grain and the kind of  FlashCopy service being used. Mapping consideration:  For multiple FlashCopy targets, you must consider the number of  mappings. For example, for a mapping with a 256 KB grain size, 8 KB of memory allows  one mapping between a 16 GB source volume and a 16 GB target volume. Alternatively,  for a mapping with a 256 KB grain size, 8 KB of memory allows two mappings between one  8 GB source volume and two 8 GB target volumes. When you create a FlashCopy mapping, if you specify an I/O Group other than the I/O  Group of the source volume, the memory accounting goes towards the specified I/O  Group, not towards the I/O Group of the source volume. The default amount of memory for FlashCopy is 20 MB. This value can be increased or  decreased by using the  chiogrp  command. The maximum amount of memory that can be  specified for FlashCopy is 2048 MB (512 MB for 32-bit systems). The maximum combined  amount of memory across all copy services features is 2600 MB (552 MB for 32-bit systems). Bitmap allocation:  When creating a FlashCopy mapping, you can optionally specify the  I/O group where the bitmap is allocated. If you specify an I/O Group other than the  I/O Group of the source volume, the memory accounting goes towards the specified I/O  Group, not towards the I/O Group of the source volume. This option can be useful when an  I/O group is exhausting the memory that is allocated to the FlashCopy bitmaps and no  more free memory is available in the I/O group. The following implementation restrictions apply to FlashCopy: Table 6-4 Relationship of bitmap space to FlashCopy address space for the specified I/O Group Copy Service Grain size in KB 1 MB of memory provides the following  volume capacity for the specified  I/O Group FlashCopy 256 002 TB of target volume capacity FlashCopy 064 512 GB of target volume capacity Incremental FlashCopy 256 001 TB of target volume capacity Incremental FlashCopy 064 256 GB of target volume capacity FlashCopy general restrictions GLYPH<SM590000> The size of source and target volumes in a FlashCopy mapping must be the same. GLYPH<SM590000> Multiple FlashCopy mappings that use the same target volume can be defined, but only  one of these mappings can be started at a time. This limitation means that no multiple  FlashCopy can be active to the same target volume. GLYPH<SM590000> Expansion or shrinking of volumes defined in a FlashCopy mapping is not allowed. To  modify the size of a source or target volume, first remove the FlashCopy mapping. GLYPH<SM590000> In a cascading FlashCopy, the grain size of all the FlashCopy mappings that participate  must be the same. GLYPH<SM590000> In a multi-target FlashCopy, the grain size of all the FlashCopy mappings that participate  must be the same. Chapter 6. Copy services  157