Table 2-2 Specifications of Extended Consistency Groups
Item
Specifications
The number of extended consistency groups that can be created | Up to four per one storage system |
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The number of journal groups that can be registered in one | Up to 16 |
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extended consistency group |
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The following explains configuration of extended consistency groups (i.e., primary and secondary EXCTGs). Note the following when configuring extended consistency groups.
Guaranteed Consistency of Data Update Sequence:
URz restores journal data to secondary data volumes by taking the following steps. The following procedure guarantees consistency of data update sequence within an extended consistency group:
a.URz checks the extended consistency group for the time stamps of all journal data that have not been restored to secondary data volumes, and then identifies the latest time stamp for each journal group.
In the example shown in Figure
•In Journal group 1, the latest time stamp is 15:00.
•In Journal group 2, the latest time stamp is 15:02.
•In Journal group 3, the latest time stamp is 15:03.
•In Journal group 4, the latest time stamp is 15:04.
b.URz searches for the oldest time stamp from the ones identified in step a and restores data up to that time to the secondary volumes.
In the example shown in Figure
•For Journal group 1, URz restores all data up to 15:00.
•For Journal group 2, URz restores all data up to 14:02.
•For Journal group 3, URz restores all data up to 14:03.
•For Journal group 4, URz restores all data up to 14:04.
Chapter 2 About Universal Replicator Operations |
