IBM DS8000 manual Data migration based on physical migration, Summary of data migration objectives

14.1.4 Summary of data migration objectives

To summarize the objective of data migration, it might be feasible to not just migrate the data from existing storage subsystems to the new storage server images, but also to consolidate source storage subsystems to one or fewer target storage servers. A second migration layer might be to consolidate multiple source volumes to larger target volumes, which is also called volume folding. The latter is in general more difficult to do and requires data migration on a data set level. Some down time is needed to move the remaining data sets, which are usually open and active 24 hours every day. If you, for example, consolidate a storage group with 1,000 volumes to 200 volumes, the service interruptions could be few and long or frequent and brief.

14.2 Data migration based on physical migration

Physical migration here refers to physical full volume operations, which in turn require the same device geometry on the source and target volume. The target volume capacity is equal to the source volume capacity or larger. The device geometry is defined by the track capacity and the number of tracks per cylinder. The same device geometry means that source and target devices have the same track capacity and the same number of tracks per cylinder. Usually this is not an issue because over time the device geometry of the IBM 3390 volume has become a quasi standard and most installations have used this standard. For organizations still using other device geometry (for example, 3380), it might be worthwhile to consider a device geometry conversion, if possible. This requires moving the data on a logical level, which is on a data set level, and allows for reblocking during the migration from 3380 to 3390.

Utilizing physical full volume operations is possible through the following software-, microcode-, and hardware-based functions:

￿Software-based

–DFSMSdss

–TDMF

–FDRPAS

￿Software- and hardware-based:

–zSeries Piper - uses currently a zSeries Multiprise® server with ESCON attachment only

–z/OS Global Mirror (XRC)

￿Hardware- and microcode-based:

–Global Mirror

–Global Copy

–FlashCopy in combination with either Global Mirror or Global Copy, or both

–Metro/Global Copy

The following section discusses DFSMSdss and the Remote Copy-based approaches in more detail.

14.2.1 Physical migration with DFSMSdss and other storage software

Full volume copy through the COPY command copies all data between like devices from a source volume to a target volume. The target volume might be bigger than the source but cannot be smaller than the source volume. You have to keep the same volume name and the same volume serial number (VOLSER) on the target volume; otherwise, the data set cannot be located any more via catalog locates. This is achieved through the COPYVOLID

298DS8000 Series: Concepts and Architecture