HP StorageWorks P9000 Tiered Storage Manager Software 7.1.1 CLI Reference Guide (TB585-96014, September 2011)

zero data discard Action of discarding and releasing zero data (unused capacity that is not being
accessed from hosts) in a migration-target THP volume after migration to a THP
volume or THP pool is completed, reducing the amount of THP pool area in use.
Zero data discard is the same as zero page reclaim in Device Manager.
CLI Reference Guide 207