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316 DS8000 Series: Concepts and Architecture
impact when the actual switch uses P/DAS, although it is quicker and easier to allow for a
brief service interruption and quickly switch to the new disk storage server. Because Metro
Mirror provides data consistency at any time, the switch-over to the new disk server is simple
and does not require further efforts to ensure data consistency at the receiving site. It is
feasible to use the GUI-based approach because migration is usually a one time effort.
Command-line interfaces such as TSO commands are an alternative and can be automated
to some extent with REXX procedures.
When the source disk servers are not compatible with the DS8000 and the migration is based
on a full volume, physical level, then there are options which depend on various
circumstances which are different for each installation. When TDMF or FDRPAS is available
and the customer is used to managing volume migration using these software tools, then it is
a likely approach to use these tools for a larger scale migration as well. In other
circumstances it might be feasible to include the migration as part of a total package when
installing and implementing DS8000 disk storage servers. This is possible through IGS
services which rely on FDRPAS, TDMF or Piper for z/OS. There is always DFSMSdss, which
is still popular, but this approach usually requires an outage of the specific application
systems.
Finally, the migration might be used as an opportunity to consolidate volumes at the same
time. After a decision has been made about the new volume size, which is preferably a
multiple of a 3390-1 or 1113 cylinders, it is required to logically move the data sets. One
option is to rely on SMS-based allocation in a system-managed environment, combined with
DFSMSdss and logical data set copies targeted from individual source volume sets or entire
SMS storage groups. A variation here might be a combination of full volume physical copy for
the very first volume copied to a larger target volume, followed by further logical-based copy
operations with DFSMSdss after adjusting the VTOC and VTOC index information.
After the migration and storage consolidation you will be using a disk storage server
technology that will serve you with promising performance and excellent scalability combined
with rich functionality and high availability.