(1) Pertaining to communication in which data can be sent and received at the same time. See also half-duplex.
(2) Pertaining to printing on both sides of a sheet of paper.
(3) Pertaining to the process of writing two sets of identical records in order to create a second copy of data.
(4) In ESS Copy Services, the state of a volume pair after Peer-to-Peer Remote Copy (PPRC) has completed the copy operation and the volume pair is synchronized.