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Chapter 13. Data Migration in zSeries environments 259
Figure 13-4 Intermediate ESS 800 used to migrate data with PPRC over ESCON
To utilize the advantage of PPRC with concurrent data migration, on a physical volume level
though, from older ESS models like the ESS F20, an ESS 800 (or in less active
configurations an ESS 750) might be used during the migration period to bridge from a PPRC
ESCON link storage server to the new disk storage server which supports only PPRC over
FCP links. The approach is Metro/Global Copy with the ESS 800 in between hosting the
cascaded volumes, which are PPRC secondary volumes for Metro Mirror and at the same
time also PPRC primary volumes for the Global Copy configuration. It is recommended that
you connect the intermediate ESS to a host whether it is over ESCON channels or FICON
channels. This allows the ESS 800 to off-load messages to the host as well as to manage the
PPRC volumes within the intermediate ESS during the migration period.
The actual setup and management might be performed through the ESS GUI with its Copy
Services application. Another possibility is to manage such a cascaded configuration with
host-based software like ICKDSF or TSO commands, when the TSO command support for
cascaded volumes is available. Otherwise use a combination of TSO commands and ICKDSF
for just defining the cascaded bit when setting up Metro Mirror between the intermediate ESS
800 and the target DS6800 disk server.
Dynamic Address Switch (P/DAS) for a non-disruptive application I/O switch from the old
hardware to the volumes in the new hardware is not possible in this configuration because
P/DAS requires the PPRC secondary volumes to be in a DUPLEX state. PPRC-XD stays per
definition always in PENDING state. Theoretically it is possible to switch from PPRC-XD to
Synchronous PPRC and replicate the data twice over Synchronous PPRC, which may
impose significant impact to write I/O to the old hardware. It is usually quicker and less
difficult, when a brief application down time is accepted, to switch from the old hardware to
the volumes in the new hardware.
Again this approach is only possible from IBM ESS to IBM DS6000 or IBM DS8000 disk
storage servers and it requires the same size or larger PPRC secondary volumes with the
same device geometry.
Data migration with Metro Mirror or Global Copy
A variation to the approach discussed above is to use straightforward Metro Mirror or Global
Copy from ESS 750 or ESS 800 to the DS6800.
FICON
DS 6000
Intermediate ESS 800
PPRC
Links
FCP
PPRC
Links
ESCON
ESS E20s
ESCON
Global Copy
Metro Mirror
Cascading
Metro/Global Copy