Note: When you issue the DEVSERV command to the URz secondary data volume, INDETERMINATE FAILING UNIT is returned, if the status of URz secondary data volume is online. INTERVENTION REQUIRED is returned, if the status of URz secondary data volume is offline.
Secondary Data Volume Write Option
For additional flexibility, URz provides a secondary data volume write option
Secondary Data Volume Read Option
For additional flexibility, URz offers a special secondary data volume read option. The Hitachi representative enables the secondary data volume read option on the secondary storage system (mode 20). The secondary data volume read option allows you to read a URz secondary data volume only while the pair is suspended, that is, without having to release the pair. The secondary storage system will allow you to change only the VOLSER of the suspended secondary data volume, so that the secondary data volume can be online to the same host as the primary data volume while the pair is suspended. All other write I/Os will be rejected by the secondary subsystem. The primary storage system copies the VOLSER of the primary data volume back onto the secondary data volume when the pair is resumed. When the secondary data volume read option is not enabled and/or the pair is not suspended, the secondary storage system rejects all read and write I/Os to a URz secondary data volume.
Difference Management
The differential data (updated by write I/Os during split or suspension) between the primary data volume and the secondary data volume is stored in each track bitmap. When a split/suspended pair is resumed (Resume Pair), the primary storage system merges the primary data volume and secondary data volume bitmaps, and the differential data is copied to the secondary data volume.
Chapter 2 About Universal Replicator Operations |
