HP Application Recovery Manager software A.06.10 Concepts guide (March 2008)

After the replica is created, the database returns to normal operation. Any subsequent
backup operations are performed on the replica, leaving the database online and
unaffected.
In both cases, the effect on the application is limited to the period during which the
replica is created, much less than with standard tape backup techniques. For online
backup, database operation is never stopped (zero downtime) and the effect on
performance can be minimal, limited mainly to the effect of having to write increased
information to the transaction logs.
Creating replicas
Replication creates a replica of application/filesystem data at a particular moment.
The volumes containing the source or original data objects to be replicated are
referred to as source volumes. These are replicated to an equivalent number of target
volumes. When the replication process is complete, the data in the target volumes
constitutes the replica.
Currently there are two basic replication techniques (described more fully in
Chapter 2 on page 21):
• Split mirror
A mirror is a dynamic duplicate of the source data, synchronized with it. Any
changes to the source are also applied to the mirror.
The technique allows a duplicate of filesystem/application data to be created
and maintained during normal application use.
To create a replica, the mirror is temporarily split from the source. Data is backed
up from the mirror and the mirror is then resynchronized with the source.
• For more details, see “Split mirror replication” on page 23.
• Snapshot
A snapshot replica is created by making a copy of data at a particular moment.
The snapshot can be a full copy, thus independent of the source volume, or a
virtual copy that still depends on the source volume.
• For more details, see “Snapshot replication” on page 25.
Instant recovery or restoring data from ZDB
Instant recovery requires a replica to exist on the same disk array on which the data
is to be restored. Application and backup systems are disabled and the contents of
Concepts guide 19