RAC One Node

How does RAC One Node compare with traditional cold fail over solutions like HP Serviceguard, IBM HACMP, Sun Cluster and Symantec, and Veritas Cluster Server?

RAC One Node is a better high availability solution than traditional cold fail over solutions.
RAC One Node operates in a cluster but only a single instance of the database is running on one node in the cluster.
If that database instance has a problem, RAC One Node detects that and can attempt to restart the instance on that node
If the whole node fails,RAC One Node will detect that and will bring up that database instance on another node in the cluster.

Unlike traditional cold failover solutions, Oracle Clusterware will send out notifications (FAN events) to clients to speed reconnection after failover.
3rd-party solutions may simply wait for potentially lengthy timeouts to expire.

RAC One Node goes beyond the traditional cold fail over functionality by offering administrators the ability to proactively migrate instances from one node in the cluster to
another.

For example, lets say you wanted to do an upgrade of the operating system on
the node that the RAC One Node database is running on. The administrator would activate
“OMotion,” a new Oracle facility that would migrate the instance to another node in the
cluster.

Once the instance and all of the connections have migrated, the server can be shut
down, upgraded and restarted.

OMotion can then be invoked again to migrate the instance and the connections back to the now-upgraded node.

This non-disruptive rolling upgrade and patching capability of RAC One Node exceeds the current functionality of the traditional cold fail over solutions.

Also, RAC One Node provides a load balancing capability that is attractive to DBAs and SysAdmins.

For example, if you have two different database instances running on a RAC One
Node Server and it becomes apparent that the load against these two instances is impacting
performance, the DBA can invoke OMotion and migrate one of the instances to another lessused
node in the cluster.

RAC One Node offers this load balancing capability, something
that the traditional cold fail over solutions do not

Lastly,many 3rd-party solutions do not support ASM storage. This can slow down failover,
and prevent consolidation of storage across multiple databases, increasing the management
burden on the DBA.
The following table summarizes the differences between RAC One Node and 3rd-party fail
over solutions:

What is Oracle Real Application Clusters One Node (RAC One Node)?

Oracle RAC One Node is an option available with Oracle Database 11g Release 2. Oracle RAC One Node is a single instance of Oracle RAC running on one node in a cluster.
This option adds to the flexibility that Oracle offers for reducing costs via consolidation.

It allows customers to more easily consolidate their less mission critical, single instance databases into a single cluster,
with most of the high availability benefits provided by Oracle
Real Application Clusers (automatic restart/failover, rolling patches, rolling OS and
clusterware upgrades), and many of the benefits of server virtualization solutions like
VMware.

RAC One Node offers better high availability functionality than traditional cold failover cluster solutions because of a new Oracle technology Omotion,
which is able to intelligently relocate database instances and connections to other cluster nodes for high availability and system load balancing.

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