HP XP7 Storage - Manual (Page 34)

Planning pairs and pair volumes
This section discusses requirements, options, and settings you need for setting up pairs and pair
volumes. You begin by:
•
Identifying data and volumes at the local site that you want to protect with a backup
•
Setting up volumes at the remote site that will hold copied data.
The following helps ensure that the pairs you create fit your requirements.
•
“Pair volume requirements and recommendations” (page 34)
•
“Precautions for duplicate VOLSERs” (page 35)
•
“About allowing I/O to the S-VOL” (page 36)
•
“Allowing I/O to the P-VOL after a split—Fence Level options” (page 36)
•
“Differential data ” (page 37)
•
“Maximum number of pairs supported” (page 37)
•
Options and settings for number of pairs copied, and their priority, during the initial copy
and resync operations. See
“Priority for initial copy operations and scheduling order” (page 38)
Pair volume requirements and recommendations
The following is provided to help you prepare Continuous Access Synchronous Z volumes:
•
A volume can be assigned to only one pair.
•
Volumes on the primary and secondary storage systems must be defined and formatted prior
to pairing.
•
The S-VOL must be equal-to or larger-than the P-VOL. However, if the S-VOL is larger than the
P-VOL, the swap operation cannot be performed.
•
Continuous Access Synchronous Z requires a one-to-one relationship between the P-VOL and
S-VOL. The P-VOL cannot be copied to more than one S-VOL, and an S-VOL cannot have more
than one P-VOL.
•
Logical Volume Images (LVIs)
All basic mainframe LVIs that can be configured on the XP7 system are supported for
Continuous Access Synchronous Z; for example, 3390 3, 3R, 9, L. ◦
◦ Multi-platform volumes (3390 3A/B/C) are not supported.
◦ Data can be copied between volumes with the same emulation and capacity (for example,
3390 3R to 3390 3R).
◦ Data can be copied from smaller volumes to larger volumes (for example, 3390 3 to
3390 9) of the same emulation (VTOC expansion must be used).
However, HP strongly recommends that you limit copying from a smaller volume to a
larger volume to data migration purposes and not disaster recovery. Under the disaster
recovery scenario, you would not be able to perform Continuous Access Synchronous Z
operations in the reverse direction, from the secondary system to the primary system,
because a larger volume cannot be copied to a smaller volume.
Also, with larger-to-smaller volumes, if the BCM SUSPEND command is issued, you cannot
use the secondary system R/W option and Reverse option.
•
Pair volumes have the following disk track format requirements. Continuous Access Synchronous
Z cannot detect exceptions to these requirements. The primary system will abort the initial
34 Planning for Continuous Access Synchronous Z