IBM Midrange System DS4000 Series Hardware Manual page 442

Returning logical drives back to their preferred paths
Once the underlying root cause of the logical drives switching to non-preferred path has been
identified and resolved, then it is possible to return them back to their normal preferred paths.
This can be done from the Storage Manager Subsystem Management window by selecting
Advanced  Recovery  Redistribute Logical Drives. Figure 7-65 shows the Redistribute
Logical Drives window with a progress bar that appears during the procedure.
Figure 7-65 Redistribute Logical Drives window
When complete, the DS4000 or DS5000 unit returns to an Optimal state in Storage Manager.
If any problems remain unresolved, the affected logical drives will fail back onto their
non-preferred paths.
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IBM Midrange System Storage Hardware Guide