A file can become fragmented when you modify a file using FlashCopy® images. To defragment the contents of an individual file without changing its assigned storage pool, use the file movement function and move the file to the same storage pool in which it currently exists.
When a file is moved, the file's extents are copied serially, one after the other. As the extents are written to the target storage pool, blocks are coalesced in order into continuous extents. Space is allocated on available volumes in the target storage pool one partition at a time. Partitions are used in around-robin fashion across volumes where space is available within the target storage pool. This causes the file's blocks to be continuous on the target LUNs in at least extent-sized units and at most partition-sized units. This eliminates fragmentation caused by FlashCopy images, and the file can use all volumes with available space in the target storage pool.
Parent topic: Storage management