IBM System Storage DS3000, Programming Manual

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label for conformance to this pattern. The CLI only permits specification of an existing logical drive for
use as a Enhanced FlashCopy repository logical drive member if that logical drive user label conforms to
the pattern.
Enhanced FlashCopy Logical drives
An Enhanced FlashCopy logical drive provides the host access to the data contained in an Enhanced
FlashCopy image. An Enhanced FlashCopy image cannot be directly read by a hosts because the
Enhanced FlashCopy image is only the changed data captured from the base logical drive. Therefore, it is
necessary to create a logical drive that a host can access that is a merging of the data from the base
logical drive and the Enhanced FlashCopy image.
The Enhanced FlashCopy logical drive can be designated as either read-only or read-write:
v
A Read-Only Enhanced FlashCopy logical drive provides a host application with READ access to a
copy of the data contained in the Enhanced FlashCopy image, but without the ability to modify the
Enhanced FlashCopy image. A Read-Only Enhanced FlashCopy logical drive does not have an
associated Enhanced FlashCopy logical drive repository.
v
A Read-Write Enhanced FlashCopy logical drive requires an associated Enhanced FlashCopy logical
drive repository to provide the host application with WRITE access to a copy of the data contained in
the Enhanced FlashCopy image.
An Enhanced FlashCopy logical drive that is designated as read-write must have its own Enhanced
FlashCopy logical drive repository logical drive to save any subsequent modifications made by the host
application to the base logical drive without affecting the referenced Enhanced FlashCopy image.
The Enhanced FlashCopy logical drive repository logical drive is allocated from the disk pool or
subsystem from which the original Enhanced FlashCopy image is allocated. All I/O write operations to
the Enhanced FlashCopy image are redirected to the Enhanced FlashCopy logical drive repository that
was allocated for saving data modifications. The data of the original Enhanced FlashCopy image remains
unchanged.
When you delete an Enhanced FlashCopy logical drive, you can either delete the Enhanced FlashCopy
logical drive repository logical drive or retain it as an unmapped logical drive.
Relationship Between Enhanced FlashCopy Images, Enhanced FlashCopy Groups,
and Enhanced FlashCopy Logical drives
The controller firmware and the IBM DS Storage Manager software management software treat Enhanced
FlashCopy images, Enhanced FlashCopy groups, and Enhanced FlashCopy logical drives as distinct
entities relative to Enhanced FlashCopies:
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An Enhanced FlashCopy group has an association with a standard logical drive that is the base for the
Enhanced FlashCopy group.
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All Enhanced FlashCopy images within an Enhanced FlashCopy group have a direct association with
that Enhanced FlashCopy group.
v Every Enhanced FlashCopy logical drive of an Enhanced FlashCopy image has a direct association
with that Enhanced FlashCopy image. In addition, every Enhanced FlashCopy logical drive has a
persistent relationship to the base logical drive of the Enhanced FlashCopy image for which the
Enhanced FlashCopy logical drive was initially created. In other words, an Enhanced FlashCopy logical
drive is effectively “bound” to its base logical drive. Even if the Enhanced FlashCopy logical drive is in
a Stopped state, which detaches from a particular Enhanced FlashCopy image, the Enhanced
FlashCopy logical drive retains its association with the base logical drive, and can only be restarted on
an Enhanced FlashCopy image for the base logical drive.
v
The Enhanced FlashCopy repository logical drives for an Enhanced FlashCopy group have an
association with the Enhanced FlashCopy group.
Chapter 6. Using the Enhanced FlashCopy Images Premium Feature
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