Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

FastResync maps on disk so that they can survive system reboots and system
crashes. When the disk groups are rejoined, this allows the snapshot plexes to be
quickly resynchronized. This ability is not supported by non-persistent FastResync.
If persistent FastResync is enabled on a volume or on a snapshot volume, a DCO
and a DCO log volume are associated with the volume.
The DCO object is used not only to manage FastResync maps, but also to manage
DRL recovery maps and special maps called copy maps that allow instant snapshot
operations to be resume following a system crash.
Persistent FastResync can also track the association between volumes and their
snapshot volumes after they are moved into different disk groups. When the disk
groups are rejoined, this allows the snapshot plexes to be quickly resynchronized.
This ability is not supported by non-persistent FastResync.
About disk group split and join
Disk group split and join is included with the Enterprise Edition. It is also included
as part of the Veritas FlashSnap option with the Standard Edition.
VxVM provides a disk group content reorganization feature that supports general
disk group reorganization and allows you to move volume snapshots to another
host for off-host backup. Additional options to the vxdg command enable you to
take advantage of the ability to remove all VxVM objects from an imported disk
group and move them to a newly created target disk group (split), and to remove
all VxVM objects from an imported disk group and move them to an imported
target disk group (join). The move operation enables you to move a self-contained
set of VxVM objects between the imported disk groups.
About hot-relocation
In addition to providing volume layouts that help improve database performance
and availability, VxVM offers features that you can use to further improve system
availability in the event of a disk failure. Hot-relocation is a feature that allows a
system to react automatically to I/O failures on mirrored or RAID-5 volumes and
restore redundancy and access to those volumes.
VxVM detects I/O failures on volumes and relocates the affected portions to disks
designated as spare disks or free space within the disk group. VxVM then
reconstructs the volumes that existed before the failure and makes them redundant
and accessible again.
The hot-relocation feature is enabled by default and is recommended for most
database configurations. After hot-relocation occurs, we recommend verifying
29Introducing Veritas Storage Foundation for Oracle
How Veritas Volume Manager works