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

2-36 About TrueCopy for z/OS Operations
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
When a TCz pair is suspended, whether user-requested or due to failure, the
MCU generates sense information to notify the host(s). If the host system
supports IBM PPRC (and the PPRC support RCU option is enabled), this
notification results in an IEA494I and/or IEA491E system console message
which indicates the reason for suspension.
Note: If you need write access to an R-VOL, you must release the pair.