VERITAS Storage Foundation 4.1 Oracle Administrator's Guide

Prerelease 8 September 2005, 8:55am
524 VERITAS Storage Foundation for Oracle Administrator’s Guide
device file
A block- or character-special file located in the /dev directory representing a device.
device name
The name of a device file. It represents a device. The c#t#d# syntax identifies the controller,
target address, and disk.
direct I/O
An unbuffered form of I/O that bypasses the kernel’s buffering of data. With direct I/O, data is
transferred directly between the disk and the user application.
Dirty Region Logging
The procedure by which the VERITAS Volume Manager monitors and logs modifications to a plex.
A bitmap of changed regions is kept in an associated subdisk called a log subdisk.
disk access name
The name used to access a physical disk, such as c0t0d0. The c#t#d# syntax identifies the
controller, target address, and disk. The term device name can also be used to refer to the disk
access name.
disk array
A collection of disks logically and physically arranged into an object. Arrays provide benefits
including data redundancy and improved performance.
disk cache
A section of RAM that provides a cache between the disk and the application. Disk cache enables
the computer to operate faster. Because retrieving data from hard disk can be slow, a disk caching
program helps solve this problem by placing recently accessed data in the disk cache. Next time
that data is needed, it may already be available in the disk cache; otherwise a time-consuming
operation to the hard disk is necessary.
disk group
A collection of disks that 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 and an internally defined unique ID. The root disk group (rootdg) is a special private disk
group that always exists.