Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

About dirty region logging
Dirty region logging (DRL), if enabled, speeds the recovery of mirrored volumes
after a system crash. DRL keeps track of the regions that have changed due to I/O
writes to a mirrored volume. DRL uses this information to recover only those
portions of the volume that need to be recovered.
Note: If a version 20 data change object (DCO) volume is associated with a volume,
a portion of the DCO volume can be used to store the DRL log. There is no need
to create a separate DRL log for a volume that has a version 20 DCO volume.
For more information on DCOs and DCO volumes, see the Veritas Volume Manager
Administrator's Guide.
About SmartSync recovery accelerator
SmartSync increases the availability of mirrored volumes by only resynchronizing
changed data. SmartSync reduces the time required to restore consistency, freeing
more I/O bandwidth for business-critical applications.
This feature is applicable only to databases that are configured on raw volumes.
If supported by the database vendor, the SmartSync feature uses an extended
interface between VxVM volumes and the database software to avoid unnecessary
work during mirror resynchronization. For example, Oracle automatically takes
advantage of SmartSync to perform database resynchronization when it is
available.
About volume sets
Volume sets are an enhancement to VxVM that allow several volumes to be
represented by a single logical mount device. All I/O from and to the underlying
volumes is directed via the I/O interfaces of the volume set. The volume set feature
supports the multi-device enhancement to Veritas File System (VxFS). This feature
allows file systems to make best use of the different performance and availability
characteristics of the underlying volumes. For example, file system metadata
could be stored on volumes with higher redundancy, and user data on volumes
with better performance.
About volume snapshots
A volume snapshot is a point-in-time image of a volume. Veritas Volume Manager
provides three volume snapshot features based on disk mirroring:
■ Full-sized instant snapshots
27Introducing Veritas Storage Foundation for Oracle
How Veritas Volume Manager works