VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Glossary 313
data change object (DCO)
A VxVM object that is used to manage information about the FastResync maps in the
DCO volume.Both a DCO object anda DCO volume must beassociated with a volumeto
implement Persistent FastResync on that volume.
data stripe
This represents the usable data portion of a stripe and is equal to the stripe minus the
parity region.
DCO volume
A special volume that is used to hold Persistent FastResync change maps.
detached
A state in which a VxVM object is associated with another object, but not enabled for use.
device name
The device name or address used to access a physical disk, such as c0t0d0. The c#t#d#
syntax identifies the controller, target address, and disk. In a SAN environment, it is more
convenient to use enclosure-based naming, which forms the device name by concatenating
the name of the enclosure (such as enc0) with the disk’s number within the enclosure,
separated by anunderscore(for example,enc0_2). The termdisk access name canalso be
used to refer to a device name.
dirty region logging
The procedurebywhich theVxVMmonitors and logs modificationsto a plex.Abitmap of
changed regions is kept in an associated subdisk called a log subdisk.
disabled path
A path to a disk that is not available for I/O. A path can be disabled due to real hardware
failures or if the user has used the vxdmpadm disable command on that controller.
disk
A collection of read/write data blocks that areindexed and can be accessed fairly quickly.
Each disk has a universally unique identifier.
disk access name
An alternative term for a device name.