Veritas Storage Foundation Cross-Platform Data Sharing 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

62 Glossary
data change object
See DCO.
DCO (Data Change Object)
A VxVM object that is used to manage information about the FastResync maps in the DCO
volume. Both a DCO object and a DCO volume must be associated with a volume to
implement Persistent FastResync on that volume.
DCO volume
A special volume that is used to hold Persistent FastResync change maps, and dirty region
logs. The map layout within the DCO volume changed with the release of VxVM 4.0,
although the original format is still available. The old layout is available in DCO Version 0
objects, and the new layout is available in DCO Version 20 objects.
device name
The physical disk device name (or disk access name).
dirty region logging
See DRL.
disk access name
The device name or address that is used to access a physical disk on an operating system,
such as hdisk1 (AIX), c0t0d0 (HP-UX), disk11 (HP-UX 11i v3 onwards), sda (Linux), or
c0t0d0s2 (Solaris OS). 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 an underscore
(for example, enc0_2).
disk group
A set of disks that are under VxVM control and share a common configuration. A disk
group configuration is a set of records containing detailed information on existing Veritas
Volume Manager objects (such as disk and volume attributes) and their relationships. Each
disk group has an administrator-assigned name. Volumes can only be created on disks that
belong to disk groups.
disk media name
A logical or administrative name chosen for a disk that is under the control of VxVM, such
as disk03. Also referred to as a disk name.
DRL (dirty region logging)
The method by which the VxVM monitors and logs modifications to a plex as a bitmap of
changed regions. For volumes with a new-style DCO volume, the dirty region log is
maintained in the DCO volume. Otherwise, the dirty region log is allocated to an associated
subdisk called a log subdisk.
encapsulation
A process that converts existing partitions on a specified disk to volumes. If any partitions
contain file systems, /etc/fstab entries are modified so that the file systems are
mounted on volumes instead. This feature is only supported on the Linux and Solaris
operating systems.
enclosure
A disk array.