HP StorageWorks XP Remote Web Console Software - Manual (Page 21)

Snapshot XP user guide 21
Using the number of pair tables
Hitachi FlashCopy Mirroring Version 2 and Snapshot XP pairs use pair tables to store control information
needed to manage pairs. To create an Hitachi FlashCopy Mirroring Version 2 or Snapshot XP pair, you
need one pair table for each pair.
Usually, up to 32,768 pair tables are available in one disk array. However, if the relationship expansion
function, which is an Hitachi FlashCopy Mirroring Version 2 function, is effective, the maximum number of
available pair tables in one disk array is 1,048,575.
Among disk array software products, only Hitachi FlashCopy Mirroring Version 2 and Snapshot XP use
pair tables. Therefore, if you use Hitachi FlashCopy Mirroring Version 2, calculate the number of available
pair tables for Snapshot XP pairs by subtracting the number of differential tables Hitachi FlashCopy
Mirroring Version 2 pairs use from the number of pair tables for the whole disk array.
For information about checking the number of pair tables Hitachi FlashCopy Version 2 uses (that is, the
number of already created Hitachi FlashCopy Version 2 pairs), see the Hitachi ShadowImage for z/OS
User Guide.
For example, when the relationship expansion function is effective and the number of pair tables Hitachi
FlashCopy Mirroring Version 2 uses is 30,000, calculate the number of Snapshot XP pairs you can create
for a disk array as follows.
32,768 - 30,000 = 2,768
According to this result, the maximum number of Snapshot XP pairs you can create 2,768.
Using Snapshot XP
This section describes the procedure for using Snapshot XP.
The first section describes the flow of Snapshot XP processes. The next section describes how the status of a
Snapshot XP pair changes while using Snapshot XP. The other sections provide information needed to
create pools and switch off the disk array’s power supply after you start using Snapshot XP.
Procedure for using Snapshot XP processes
Figure 3 Procedure for using Snapshot XP
To create pools and V-VOLs, use Command View XP or XP Remote Web Console. To create Snapshot XP
pairs and perform subsequent operations, use RAID Manager. You can also use Command View XP or XP