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Chapter 3 Preparing for Universal Replicator z/OS Operations 3-11
Hitachi Universal Replicator for IBM /OS User’s Guide
Journal Group
The URz journal groups have the following requirements:
• Each URz pair must be assigned to one and only one journal group. Table
3-9 shows the journal group specifications.
Table 3-9 Journal Group Specifications
Item Support specifications
Number of journal groups
Up to 256 journal groups (No. 0 - 255) per one disk subsystem
Note: The recommended number of journal groups is up to 16.
Number of data volumes in a journal
group
Up to 4,096
Number of journal volumes in a journal
group
Up to 64
Number of Mirror IDs
Up to 4 (ID No.: 0 to 3)
Note: If TCz Sync. uses No. 0, No. 1 to 3 are available for URz.
The same number of journal volumes is not required in the master journal
group and the restore journal group that are paired.
Mirror ID is required for the configuration that will be supported in the future
within the 3-data center (3DC), including the expected future enhancement to
enable the user to pair one master journal group with two or more restore
journal groups. Each pair relationship in a journal group is called "Mirror".
Mirror ID identifies two or more mirrors that one journal group has. The same
Mirror ID of the journal group is applied to the data volume pair. See section
TCz Synchronous (3DC Cascading Configuration) for 3DC configurations.
• Table 3-10 shows the specifications of relationship between the data
volumes, between the journal volumes, and between the data volumes and
journal volumes in a journal group.
Table 3-10 Journal Group Volume Specifications
Item Support specifications
Emulation
type
Same emulation type.
Volume
capacity
Does not matter whether the capacity is the same or different.
CLPR
Journal volumes and data volumes in the same journal group can belong to different CLPRs.
Journal volumes must belong to the same CLPR. Data volumes must also belong to the same
CLPR.
Note: A primary journal group and the corresponding restore journal group need not belong to the
same CLPR.
Note: When URz and UR coexist in the same USP V storage system, each
journal group must contain either URz pairs or UR pairs (not both).