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

2-8 About TrueCopy for z/OS Operations
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Pairs (M-VOLs and R-VOLs)
TrueCopy for z/OS performs remote copy operations for pairs established by
the user. Each TCz pair consists of one main volume (M-VOL) and one remote
volume (R-VOL) which are located in different storage systems. The TCz M-
VOLs are the primary volumes which contain the original data, and the TCz R-
VOLs are the secondary or mirrored volumes which contain the backup or
duplicate data. The main and remote volumes must have the same format and
capacity.
During normal TCz operations, the M-VOL remains available to all hosts at all
times for read and write I/O operations. The RCU rejects all I/Os to an R-VOL.
The R-VOL read option
allows read-only access to a TCz R-VOL while the pair
is suspended.
TrueCopy for z/OS supports a maximum of 32,768 pairs (entire USP V RCU). If
the command device for Business Continuity Manager is defined, the TCz pair
can be created up to 32,767 pairs. TCz supports the basic logical volume
images (LVIs) available on the USP V (e.g., 3390-3, 3390-3R, 3390-9).
Caution: Do not use M-VOLs or R-VOLs from hosts that have different CU
emulation types (2105 or 2107, and 3990) at the same time. If you use the M-
VOLs or R-VOLs from the 2105 or 2107, and 3990 hosts simultaneously, an
MIH message might be reported to the 3990 host.