HP StorageWorks XP Remote Web Console Software - Manual (Page 13)

ShadowImage for z/OS user guide 13
1 ShadowImage for the
XP128/XP1024/XP10000/XP12000
ShadowImage (SI390) is a storage-based hardware solution for duplicating logical volumes that reduces
backup time and provides point-in-time backup. The SI390 source volumes (S-VOLs) contain the original
data and the SI390 target volume(s) (T-VOLs) contain the duplicate data. The user can choose to make up
to three copies of each S-VOL. Because each T-VOL is paired with its S-VOL independently. Each T-VOL can
be maintained as an independent copy set that can be split, resynchronized, and deleted separately from
the other T-VOLs assigned to the same S-VOL.
ShadowImage Components
SI390 operations involve the source and target volumes in the XP128/XP1024/XP10000/XP12000,
Command View XP or XP Remote Web Console, and optionally, the IBM PPRC® host software functions.
The SI390 system components are:
• SI390 volume pairs (S-VOLs and T-VOLs) (see page 13)
• Command View XP or XP Remote Web Console
• (Optional) IBM PPRC host software functions (see page 15)
• (Optional) IBM DFSMSdss host software functions (see page 15)
Figure 1 shows a typical ShadowImage configuration.
Figure 1 ShadowImage for z/OS configuration
Volume Pairs (S-VOLs and T-VOLs)
The XP128/XP1024/XP10000/XP12000 contains and manages both the original and copied SI390
data. SI390 supports a maximum of 8,192 volumes (4,096 pairs: 4,096 S-VOLs and 4,096 T-VOLs).
SI390 performs internal copy operations for logical volume pairs established by the user. Each SI390 pair
consists of one source volume (S-VOL) and up to three target volumes (T-VOLs) that are located in the same
XP128/XP1024/XP10000/XP12000. The SI390 S-VOLs are the source volumes that contain the original
data. The SI390 T-VOLs are the target or secondary (mirrored) volumes that contain the backup data. Each
T-VOL must be paired with only one S-VOL. During normal SI390 operations, the S-VOLs remain available
to all hosts at all times for read and write I/O operations. The T-VOLs become available for host access
only after a split operation has been performed.