IBM Midrange System DS4000 Series Hardware Manual page 258

3. Make sure that the correct logical volume is selected, and click the lower box to enable the
value, as shown in Figure 4-105.
Figure 4-105 Enabling pre-read redundancy check
Expanding logical drives
It is also possible to increase the size of logical drives. This action is called
Expansion
drives might be increased using one or both of the following capacities:
Free capacity available on the array of the standard or FlashCopy repository logical drive
Unconfigured capacity (in the form of unused drives) on the array of the standard or
FlashCopy repository logical drive
Increasing the capacity of a FlashCopy repository logical drive does not increase the capacity
of the associated FlashCopy logical drive. The FlashCopy logical drive's capacity is always
based on the capacity of the base logical drive at the time the FlashCopy is created.
Note: Storage Manager provides support for logical drives greater than 2 TB. This
improves the capacity requirement for applications that requires large capacity logical
drives.
Note: Increasing the capacity of a standard logical drive is only supported on certain
operating systems. If the logical drive capacity is increased on a host operating system that
is not supported, the expanded capacity will be unusable and the original logical drive
capacity will not be able to be restored.
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(DVE). The capacity of standard logical drives and FlashCopy repository logical
Dynamic Volume