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

3-6 Preparing for TrueCopy for z/OS Operations
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Duplicate VOLSER
The TrueCopy for z/OS initial copy operation copies the VOLSER of the M-VOL
to the R-VOL, if the No Copy initial copy option is not selected. For this
reason, the M-VOL and R-VOL of a TCz pair must have the same VOLSER.
Since the host OS does not allow duplicate VOLSERs, the host system
administrator must take precautions to prevent system problems related to
duplicate VOLSERs. For example, the TCz R-VOLs must be defined in the
system generation so they do not come online automatically (see WARNING
below).
WARNING: If the volumes which will become TCz R-VOLs are physically
attached to the same system images as the production volumes which will
become the TCz M-VOLs, the following problems can occur:
• When a TCz pair is established using the TSO CESTPAIR command, the
secondary volume might be online (PPRC allows this; TCz does not*). This
could produce a duplex secondary online to a host image, the results of which
are not predictable.
• When a TCz pair is released, the old secondary volume is usually offline. If a
host image is IPL’d, the operator will be offered both volumes and asked
which volume should be left offline – the old duplicate volser message. This
can be confusing and is prone to error. To avoid duplication of VOLSER, first
you must identify the volumes that will not be accessed by the host system.
Next, you must perform CHP OFF or some other operation to ensure that the
volumes are inaccessible. After that, when performing IPL, you must perform
LOAD CLEAR.
To avoid these problems, Hitachi strongly recommends that the user specify
OFFLINE=YES if the secondary volumes are to be generated in the production
host’s IOCP and system generation.
*Note: If you cannot create a pair because the TCz R-VOL is online with hosts,
all paths must be offline from all hosts. If you cannot identify the hosts that
are online, please contact your Hitachi account team. You can obtain the
information about online paths from SSBLOG of SVP.