[1] The Hitachi Data Systems implementation providing similar function was branded as ShadowImage.
Although the copy or “flash” of a volume occurred instantaneously, the FlashCopy commands were issued sequentially and the ESS required a brief moment to establish the new pointers.
Because of this minute processing delay, the data residing on two volumes that were FlashCopied are not exactly time consistent.
[2] FlashCopy Version 2 introduced the ability to flash individual data sets and then added support for “consistency groups”.
[2] FlashCopy consistency groups are used in a single-site scenario in order to create a time-consistent copy of data that can then be backed-up and sent off site, or in a multi-site Global Mirror for ESS implementation to force time consistency at the remote site.