Supported mainframe features
229
Mainframe Features and Support
Compatible Native
Flash for Mainframe
Compatible Native Flash for Mainframe provides support for IBM
FlashCopy in order to meet IBM-specific replication requirements. It
is a product that enables the making of point-in-time, full volume
copies of data, with the copies immediately available for read or write
access. You can use the copy with standard backup tools that are
available in your environment to create backup copies on tape. It also
supports dataset and extent-level copying in the same manner. DMX
support for FlashCopy uses IBM 2107 control unit emulation.
FlashCopy support is a separately licensed feature.
This product adds support for NOCOPY on non-write access. In the
initial implementation, reads from the target in NOCOPY mode
would cause copies from the source to the target. This overhead has
been removed, and users should experience generally improved
subsystem performance in situations where NOCOPY relationships
are used extensively.
Compatible Native Flash for Mainframe adds support for
Asynchronous Copy on First Write. ACOFW enables improved host
performance with the elimination of the copy-on-first-write penalty
associated with the use of Compatible Native Flash for Mainframe
(CNFM). The elimination of the COFW penalty results in a
significant improvement in general host response times.
This product has added support for FlashCopy Fast Reverse Restore
(FRR) functionality. FRR copies the target back to the source. FRR
physically copies from the target to the source those tracks that were
previously physically copied to the target while the Fast Reverse
Restore relationship was enabled. It is possible to have multiple
targets and use Fast Reverse Restore to restore any ONE of them.
The one consideration for using Fast Reverse Restore on one of the
relationships is that prior to the Fast Reverse Restore, all other targets
must be removed.
Compatible Native Flash for Mainframe adds support for FlashCopy
Commands issued to aliases. The FlashCopy specification from IBM
states that FlashCopy commands (CCW’s) must be issued to the base
address of a volume only. However, the DS8000 accepts FlashCopy
commands to the alias addresses and z/OS will use an alias address
if the base is busy. There may be a slight performance improvement
due to this change in extremely busy systems, however, it is doubtful
that it would be noticed in most situations.
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