HP StorageWorks XP Remote Web Console Software - Manual (Page 23)

Figure 5 Selecting and Settling Journal at the Secondary Subsystem
The secondary subsystem settles and restores the journal data to the secondary data volume as
follows:
•
Journal data stored in the cache
The journal data is copied to the corresponding cached track and promoted to formal data.
•
Journal data stored in the restore journal volume
The journal data is read from the restore journal volume to cache. The journal data that is
read to cache is copied to the existing cache track and promoted to formal data. After that,
the space for the restore journal volume is released.
Types of Journals
In addition to the journal data for updating, the primary subsystem sends control information to
the secondary subsystem. This control information indicates when volume pair status changes and
when a primary subsystem power-off sequence is initiated, and also maintain sequence numbers
in periods of low host activities.
Journal Group Operations
URz journal groups enable update sequence consistency to be maintained across a journal group
of volumes. The primary data volumes and secondary data volumes of the pairs in a journal group
must be located within one physical primary storage system and one physical secondary storage
system (1-to-1 requirement).
When more than one data volume is updated, the order that the data volumes are updated is
managed within the journal group that the data volumes belong to. Consistency in data updates
is maintained among paired journal groups. URz uses journal groups to maintain data consistency
among data volumes.
This section describes the following journal group operation options available in URz:
•
Timer type option
•
Journal group operations
Journal Group Operations 23