Chapter 10. Copy services 491
In addition, it allows you to manage frequent, near-instant, nondisruptive, application-aware
backups and restores using integrated application and VMware snapshot technologies. IBM
Spectrum Protect Snapshot can be widely used in both IBM and non-IBM storage systems.
To watch a video on how IBM Spectrum Protect Snapshot can help your business, see:
https://ibm.biz/Bdsjv7
10.2 FlashCopy functional overview
FlashCopy works by defining a FlashCopy mapping that consists of one source volume with
one target volume. Multiple FlashCopy mappings (source-to-target relationships) can be
defined, and point-in-time consistency can be maintained across multiple individual mappings
by using Consistency Groups. For more information, see “Consistency Group with Multiple
Target FlashCopy” on page 495.
Before you start a FlashCopy (regardless of the type and options specified), you must issue a
prestartfcmap or prestartfcconsistgrp command, which puts the cache into write-through
mode and provides a flushing of the I/O currently bound for your volume. After FlashCopy is
started, an effective copy of a source volume to a target volume is created.
The content of the source volume is presented immediately on the target volume and the
original content of the target volume is lost. This FlashCopy operation is also referred to as a
time-zero copy (T0).
The source and target volumes are available for use immediately after the FlashCopy
operation. The FlashCopy operation creates a bitmap that is referenced and maintained to
direct I/O requests within the source and target relationship. This bitmap is updated to reflect
the active block locations as data is copied in the background from the source to the target,
and updates are made to the source.
For more information about background copy, see 10.3.5, “Grains and the FlashCopy bitmap”
on page 497.
Tip: Rather than using prestartfcmap or prestartfcconsistgrp, you can also use the
-prep parameter in the startfcmap or startfcconsistgrp command to prepare and start
FlashCopy in one step.
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