HP XP7 Storage - Manual (Page 26)

•
Review journal specifications in “System requirements” (page 16) .
•
A journal can contain a maximum of 2 journal volumes.
Planning journal volumes
In addition to sizing journal volumes, you must also be aware of the following requirements and
restrictions.
•
Only THP V-VOLs whose emulation type is OPEN-V can be used for journal volumes.
•
A journal ID can be used in only one virtual storage machine.
•
Volumes to which a path is set from a host cannot be registered as journal volumes.
•
Journal volumes must be registered in a journal before the initial copy operation is performed.
•
Journal volumes must be registered on both the primary and secondary systems.
•
You can register two journal volumes in a journal in each primary storage system and secondary
system. Though two can be registered, only one is used (the first one registered). The second
is not used unless needed for maintenance, or to replace the first one.
•
Primary and secondary EXCTGs must be set up and journals registered to them before
registering journal volumes in journals.
•
Journal volumes should be sized according to RPO and write-workload. See “Sizing journal
volumes ” (page 24) for more information.
•
Journal volumes in a journal can have different capacities.
•
A master journal volume and the corresponding restore journal volume can have different
capacities.
•
The number of journal volumes in the master journal does not have to be equal to the number
of volumes in the restore journal.
•
A data volume and its associated journal volume can belong to only one journal.
•
Data volumes and journal volumes in the same journal must belong to the same controller.
•
Do not register a volume to a journal during quick formatting. Doing so stalls the operation.
•
Journal volume capacity is not included in accounting capacity.
•
Journal volumes consist of two areas: One area stores journal data, and the other area stores
metadata for remote copy.
See the following for more information about journals and journal volumes:
•
The “Journals” item in “System requirements” (page 16)
•
“Planning journals ” (page 25)
•
“Data and journal volume specifications” (page 27)
Host I/O time stamp
The I/O time stamping function must be installed on the host processor at the local site in order to
provide data consistency in Cnt Ac-J Z journals. The I/O time stamp, which is provided by MVS
DFSMSdfp, is the same time stamp that is used by Compatible XRC pairs. The I/O time stamping
function should also be installed on the host processor at the remote site, so that time stamps can
be used when copying data in the reverse direction.
If the system at the local and/or remote site consists of several CPU complexes, a SYSPLEX timer
is required to provide a common time reference for the I/O time stamping function.
26 Planning volumes, XP7 systems