Veritas Storage Foundation™ for Oracle 5.0.1 Administrator's Guide

■ Space-optimized instant snapshots

■ Emulation of third-mirror snapshots

See “About Veritas Database FlashSnap” on page 224.

About Veritas FastResync

Veritas FastResync (previously called Fast Mirror Resynchronization or FMR) is

included with the Enterprise Edition. It is also included as part of the Veritas

FlashSnap option with the Standard Edition.

Veritas FastResync performs quick and efficient resynchronization of stale mirrors

(mirrors that are not synchronized). This increases the efficiency of the VxVM

snapshot mechanism, and improves the performance of operations such as backup

and decision support. Typically, these operations require that the volume is

quiescent, and that they are not impeded by updates to the volume by other

activities on the system. To achieve these goals, the snapshot mechanism in VxVM

creates an exact copy of a primary volume at an instant in time. After a snapshot

is taken, it can be accessed independently of the volume from which it was taken.

Veritas Storage Foundation for Oracle Enterprise Edition includes a feature called

Database FlashSnap, which takes advantage of the FastResync and disk group

split and join features. Database FlashSnap provides a quicker and easier way for

database administrators to use volume snapshots.

See “How Veritas Volume Manager works” on page 20.

See “How Veritas Database FlashSnap works” on page 38.

How non-persistent FastResync works

Non-persistent FastResync allocates its change maps in memory. When

non-persistent FastResync is enabled, a separate FastResync map is assigned for

the original volume as well as for each snapshot volume. Unlike a dirty region log

(DRL), these maps do not reside on disk nor in persistent store. The advantage is

that updates to the FastResync map have little impact on I/O performance, as no

disk updates need to be performed. However, if a system is rebooted, the

information in the map is lost, so a full resynchronization is required when

performing a snapback operation. This limitation can be overcome for volumes

in cluster-shareable disk groups, provided that at least one of the nodes in the

cluster remains running to preserve the FastResync map in its memory.

How persistent FastResync works

Non-persistent FastResync has been augmented by the introduction of persistent

FastResync. Unlike non-persistent FastResync, Persistent FastResync keeps the

Introducing Veritas Storage Foundation for Oracle

How Veritas Volume Manager works