Hitachi Universal Replicator for z/OS User Guide: HP XP12000 Disk Array, HP XP10000 Disk Array, HP 200 Storage Virtualization System (T1778-96021, May 2011)

should also be installed on the host processor at the secondary site, so that time-stamps can be
used when copying data in the reverse direction.
If the system at the primary and/or secondary site consists of several CPU complexes, a SYSPLEX
timer is required to provide a common time reference for the I/O time-stamping function.
Error Reporting Communications (ERC)
Error reporting communications (ERC), which transfers information between host processors at the
primary and secondary sites, is a critical component of any disaster recovery effort. You can
configure ERC using channel-to-channel communications, NetView technology, or other interconnect
technologies, depending on your installation requirements and standards. Neither URz nor the
URz remote console software provides ERC between the primary and secondary sites.
When URz is used as a data migration tool, ERC is recommended but is not required. When URz
is used as a disaster recovery tool, ERC is required to ensure effective disaster recovery operations.
When a URz pair is suspended due to an error condition, the primary storage system generates
sense information which results in an IEA491E system console message. This information should
be transferred to the primary site via the ERC for effective disaster detection and recovery.
Remote Copy Operations
Figure 4 (page 18) illustrates the two types of URz remote copy operations: initial copy and update
copy.
Figure 4 Remote Copy Operations
This section describes the following topics that are related to remote copy operations with URz:
• Initial Copy Operations
• Update Copy Operation
• Read and Write I/O Operations During URz Operations
• Secondary Data Volume Write Option
• Secondary Data Volume Read Option
• Difference Management
18 Overview of Universal Replicator for Mainframe Operations