HP XP Continuous Access Software - Manual (Page 17)

You cannot define paths from hosts to journal volumes. This means that hosts cannot read from
and write to journal volumes.
Journal volume areas
A journal volume consists of a metadata area and a journal data area. The ratio of the metadata
area to the journal data area is the same on all journal volumes within the journal group.
Metadata that manages the journal data is stored in the metadata area. For more information
about the metadata area, see
Table 2 (page 23) . Journal data that the metadata manages is stored
in the journal data area.
NOTE: If the metadata or journal data cannot be stored for a given length of time because the
metadata or journal data areas are full with metadata or journal data that has not been discarded,
the pair is suspended. Use an XP Command View Advanced Edition Software management station
or XP Remote Web Console to specify this timeout period (Data overflow watch) as a journal group
option. This timeout period must be within the range of 0 to 600 seconds. For more information,
see
Changing options for journal groups .
Consistency groups
XP Continuous Access Journal consistency group numbers are equivalent to XP Continuous Access
Asynchronous consistency group numbers. Therefore, you can create an XP Continuous Access
Journal pair with consistency group numbers from XP RAID Manager as is the case with XP
Continuous Access Asynchronous. In XP Continuous Access Journal operations, consistency group
numbers specified from XP RAID Manager are assigned to the journal group numbers.
Consistency group number specifications are different from journal group number specifications.
Each array has the ability to manage a total of 128 consistency groups for the primary and
secondary data volumes (No. 0 to 127 are assigned).
NOTE: The consistency group number of primary and secondary data volumes to be paired must
be the same.
NOTE: When XP Continuous Access Journal and Hitachi Universal Replicator™ for z/OS coexist
in the same local array, the consistency group number must be different from the XP Continuous
Access Asynchronous consistency group number.
Figure 4 (page 18) shows the corresponding consistency group and journal group numbers.
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