HP XP Continuous Access Software - Manual (Page 20)

Adding journal volumes during a remote copy operation may not change the journal data
usage rate until the journal volumes are used. To check the journal data usage rate, use the
Usage Monitor window (see
“Usage Monitor Operations” (page 197) ).
•
Deleting journal volumes:
You can delete journal volumes under any of the following conditions:
◦ When the journal group does not contain data volumes (that is, before you create a data
volume pair for the first time in the journal group, or after all data volume pairs are
released)
◦ When all data volume pairs in the journal group are suspended
You can use Remote Web Console computers 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
The journal volume consists of the metadata area and the journal data area. The ratio of metadata
area to journal data area is common in the journal volumes within the journal group. In the metadata
area, the metadata that manages the journal data is stored. For further information on the metadata
area, see
“Metadata Information” (page 25) . The journal data that the metadata manages is stored
in the journal data area.
If the journal data cannot be stored for the length of time specified as the timeout period (data
overflow watch) because the journal data area is full, the journal group is suspended with an error.
Users can use the Remote Web Console computer to specify the timeout period as a journal group
option. The timeout period must be between 0 and 600 seconds. For details on journal group
options, see
“Changing Options for a Journal Group” (page 167) .
If the meta data area becomes full before the timeout period, the journal group is suspended with
an error.
In the multi target configuration of three XP Continuous Access Journal sites, when the free space
of the journal data area or meta data area decreases to a constant amount, one mirror in a journal
group is suspended with an error regardless of the timeout period (data overflow watch).
Host Failover Software
Host failover software, which transfers information between host servers at the primary and remote
sites, is a critical component of any disaster recovery effort. Host failover is configured using the
desired host failover software product for the platform (for example, Microsoft Cluster Server),
depending on your installation requirements and standards. The Remote Web Console software
products do not provide any host failover functions.
When XP Continuous Access Journal is used as a data migration tool, host failover is recommended,
but not required. When XP Continuous Access Journal is used as a disaster recovery tool, host
failover is required to ensure effective disaster recovery operations. When an XP Continuous Access
Journal pair is suspended due to an error condition, the primary storage system generates sense
information that should be transferred to the remote site via the host failover software for effective
disaster detection and recovery.
20 About XP Continuous Access Journal Operations