HP StorageWorks XP Remote Web Console Software - Manual (Page 20)

20 Continuous Access XP Journal
If you add a journal volume when a remote copy operation is in progress (that is, when at least one
data volume pair exists for data copying), the journal volume’s metadata area (see ” Journal volume
areas ” on page 20) is unused, and only the journal data area is used. To make the metadata area
usable, split (suspend) all data volume pairs in the journal group, and restore (resynchronize) the pairs.
Adding journal volumes during a remote copy operation does not decrease the metadata usage rate if
the metadata usage rate is high.
Adding journal volumes during a remote copy operation might not change the journal data usage rate
until the journal volumes are used. To check the journal data usage rate, use the Usage Monitor pane
(see ” Monitoring remote copy operations ” on page 124).
• Deleting journal volumes
You can delete journal volumes under any of the following conditions:
• The journal group does not contain data volumes (that is, before creating a data volume pair for the
first time in the journal group or after all data volume pairs are deleted)
• All data volume pairs in the journal group are suspended
You can use Command View XP computers or XP Remote Web Console to delete journal volumes.
• Access from hosts to journal volumes
If a path is defined from a host to a volume, you cannot register the volume as a journal volume.
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 3 on page 25. 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 Command View XP 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 ” on page 99.
Consistency groups
Continuous Access XP Journal consistency group numbers are equivalent to Continuous Access XP
Extension (asynchronous) consistency group numbers. Therefore, you can create an Continuous Access XP
Journal pair with consistency group numbers from RAID Manager as is the case with Continuous Access XP
(asynchronous). In Continuous Access XP Journal operations, consistency group numbers specified from
RAID Manager are assigned to the journal group numbers.
Consistency group number specifications are different from journal group number specifications. One disk
array has 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 the primary and secondary data volumes to be paired must be
the same.
NOTE: When Continuous Access XP Journal and Universal Replicator for z/OS coexist in the same local
disk array, the consistency group number must be different from the Continuous Access XP Extension
(asynchronous) consistency group number.