HP StorageWorks XP Remote Web Console Software - Manual (Page 27)

Journal Group Operations
Universal Replicator for Mainframe 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. Universal Replicator for Mainframe uses journal groups
to maintain data consistency among data volumes.
This section describes the following journal group operation options available in Universal Replicator
for Mainframe:
•
Timer type option
•
journal group operations
Timer Type Option
The timer type option allows you to specify the method applied by the primary storage system to
acquire the time-stamp information for each journal data. The following timer types are available
for selection:
•
System. When the System timer option is selected, the primary storage system acquires the
time-stamp information for each journal data as follows. When a Universal Replicator for
Mainframe pair is established, the primary storage system reports state-change-interrupt (SCI)
to all hosts. The host then issues a series of sense group commands to determine the device
status change, and the primary storage system returns the same response as if the device had
been added to an XRC session to activate I/O time-stamping for the device.
Once I/O time-stamping is activated, the MVS IOS routine attaches the time-stamp information
(contents of TOD clock) to each write I/O operation for the device. The time-stamp indicates
the time that the update was generated during SSCH at the main host system, and the
time-stamp is transferred to the primary storage system at the beginning of each I/O operation.
The System timer option is required for all JNLGs in an EXCTG.
•
Local. When the Local timer option is selected, the primary storage system does not acquire
time-stamp information from the host I/O time-stamping function.
•
None. This timer option can be selected only when the copy direction of a Universal Replicator
for Mainframe volume pair is in reverse direction (that is, from the secondary site to the primary
site).
When the None option is selected, the primary storage system acquires time-stamp information
from the host I/O time-stamping function.
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