Journal Copy
Journal copy is the function to copy the data in the master journal volume at the primary site to the restore journal volume at the secondary site. The secondary storage system issues the read journal command to the primary storage system to request to transfer the data that is stored in the master journal volume according to the pair create or Resume Pair operation instruction from the primary site. The primary storage system transfers the data in the journal volume to the secondary site according to the read journal command if it has the journal data that should be sent. If the primary storage system does not have the journal data, the information is sent. The secondary storage system stores the journal volume data that is sent from the primary site in the restore journal volume at the secondary site. The read journal commands are issued repeatedly and regularly from the secondary site to the primary site until the journal operation is stopped. After the data are restored, the journal sequence numbers are informed from the secondary site to the primary site when the read journal command is issued. According to this information, the journal data at the primary site are discarded.
Journal Restore
Journal restore is the function to reflect the stored data in the restore journal volume to the secondary data volume at the secondary site. The data in the restore journal volume are restored to the secondary data volume according to the write sequence number. This will ensure the write sequence consistency between the primary and secondary data volumes. After the journal data are restored to the secondary data volume, the journal data are discarded at the secondary site.
Components
URz operations involve the USP V storage systems at the primary and secondary sites, the physical communications paths between these storage systems, and the USP V URz remote console software. URz copies the original online data at the primary site to the offline backup volumes at the secondary site via the dedicated
Note: Host failover software is required for effective disaster recovery with URz.
For management of URz journal groups that consist of journal volumes located in multiple storage systems, host I/O time stamping function (provided by MVS DFSMSdfp) is a requisite functional item. An error reporting communications (ERC) feature is essential for URz to be able to recover data lost in a disaster.
Figure 2-2 shows the URz components and their functions:
Chapter 3 Preparing for Universal Replicator z/OS Operations |
