Hitachi TrueCopy for IBM z/OS User and Reference Guide (T5211-96001, June 2007)

2-40 About TrueCopy for z/OS Operations
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
• The M-VOL records updated by host-requested write I/Os after the pair was
suspended (same function as for TCz Synchronous pairs). When a suspended
TCzA pair is resynchronized, the contents of the RCU’s differential data are
sent to the MCU and merged into the MCU’s differential data. The MCU then
performs the resync operation according to the merged differential data. This
ensures that all tracks containing recordsets that were discarded are
resynchronized at this time.