HP StorageWorks XP Remote Web Console Software - Manual (Page 22)

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 31) . 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 by the timeout period (data
overflow watch) because the journal data area is full, the journal group is suspended with an error.
The Remote Web Console computer can be used 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 173) .
If the meta data area becomes full before the timeout period expires, the journal group is suspended
with an error.
Journal Group
A journal group consists of two or more data volumes and journal volumes. It is a feature that
allows you to sort multiple data volumes and journal volumes into collective units to tailor Universal
Replicator for Mainframe to meet your unique business needs. The journal group in the primary
storage system is referred to as the master journal group. The journal group in the secondary
storage system is referred to as the restore journal group. The data volumes in the master journal
group are also called the primary data volumes. The journal volumes in the master journal group
are called the master journal volumes. The data volumes in the restore journal group are similarly
called the secondary data volumes. The journal volumes in the restore journal group are called
the restore journal volumes.
The data update sequence from the host is managed per the journal group. The data update
sequence consistency between the master and restore journal groups to be paired is maintained
and ensured. The master and restore journal groups are managed according to the journal group
number. The journal numbers of master and restore journal groups that are paired can be different.
One data volume and one journal volume can belong to only one journal group.
CAUTION: Data volumes and journal volumes that belong to different LDKCs cannot coexist in
the same journal group.
For detailed information about specifying journal groups, see “Journal Group Specifications”
(page 59) .
Extended Consistency Groups
To maintain data consistency while performing remote copy operations between more than one
primary storage system and more than one secondary storage system, you must register journal
groups in an extended consistency group (abbreviated as EXCTG). An extended consistency group
is a collection of journal groups. This manual uses the term primary EXCTG to refer to an extended
consistency group for the primary storage systems and uses the term secondary EXCTG to refer to
an extended consistency group for the secondary storage system.
A secondary EXCTG must be configured to maintain data consistency if you perform remote copy
operations between more than one primary and secondary storage system. Because you need to
reverse the primary and secondary sites if a failure occurs, it is recommended that a primary EXCTG
also be configured. While you can register the journal groups of up to four different storage systems
in the same extended consistency group, you cannot register one journal group in different extended
consistency groups. The following table explains specifications of extended consistency groups.
22 About Universal Replicator for Mainframe Operations