HP StorageWorks XP Remote Web Console Software - Manual (Page 34)

On-demand copy may not always be executed when there is a Read request from the host. In that
case, the host will directly read the S-VOL data instead of the T-VOL data.
CAUTION: When the NOCOPY mode is selected, even if all the data in the S-VOL is copied to
the T-VOL by the on-demand copying process, Version 2 does not automatically withdraw the
relationship. Therefore, when you select NOCOPY mode, you must first withdraw the pair by using
the FCWITHDR command. If you select the NOCOPY2COPY mode for the relationship made by
NOCOPY mode, the background copying process is performed. When all the data is copied, the
relationship is released automatically.
Copying by Volume
If you do not specify the extent when you establish a relationship, the entire volume will be copied.
This is called volume copying. Note that to perform volume copying, the capacity of the copy
source volume must be equal to or larger than the capacity of the copy target volume.
Copying by Dataset
If you specify an extent when you establish a relationship, only a part of the volume will be copied.
This is called dataset copying. Dataset copying establishes the relationship only to the specified
extent or extents. You can specify up to 16 target extents per source extent. To perform dataset
copying, the number of tracks of the copy source extent and the copy target extent must be the
same.
The following lists identify the combinations of extents that are available or unavailable for
establishing the relationships for dataset copying in Version 2:
•
Version 2 can perform dataset copying when:
The position of the copy source extent is different from the position of the copy target
extent ◦
◦ The volume of the copy source extent is different from the volume of the copy target extent
◦ The copy source extent and the copy target extent are in the same volume, provided that
they do not overlap
◦ The data in a single source extent is to be copied simultaneously to multiple target extents
◦ Volume copying is also performed simultaneously in the same sourced volume
◦ Two source extents overlap, or one of them is an inclusive part of the other (see “Overlap
of Copy Source Extents” (page 35) ), provided that the number of overlapping extents in
each overlapped area is not more than 16 extents
34 About Version 2 Operations