Difference between RacDatabase and Standby Database

[adda.road@yahoo.com]

Hi All,

Please anyone clarify my doubt.

Having Rac Database provides failover protection.

Standby Databases also Provide Failover protection (Primary fails Failover to secondary).

In this case what is the use of having both?

Could anyone please explain me is there extra benifits having both?

I we have both , which one takes precedence?

I am confusing between these two .please explain me the details.

thanks in advance.


Rampa

[peterx]

hi,

RAC can protect any one nodes failure.
Data, DB Service (connection string) will not affect. Also can have load balancing within all nodes.

Data Guard protect data by replication, eg. DR site replication
If one site failure, like natural disaster, earthquake.
Data Guard can protect data by replicated data to another location. IP, connection string will be changed.

[Tim...]

Hi.

The difference between them blurs depending on your setup and requirement. The short answer is:

- RAC is a high-availability solution. If a node fails your system can keep running with no noticeable effect on the application layer (insert numerous caveats. ). It is a normal part of administration to take nodes offline with no detrimental affect on the configuration. In addition to its high-availability use, it may also be considered a performance feature as it allows clusters of smaller servers to form a very large database server at a fraction of the cost of one massive server (caveats againt).

- Data Guard (Standby Database) is a disaster recovery solution. Although you can perform a graceful switchover for administration purposes, it is by no means considered a "normal" task. For the most part, people have a standby database for a proper disaster situation, like a whole RAC goes down.

Cheers

Tim...

[adda.road@yahoo.com]

Hi Tim & Peter ,

Thank you so much for reply.
I understand the concept.

Once again thanks.

Rampa

[Tim...]

[adda.road@yahoo.com]

Hi Tim,

If one node goes down ,Rac protect the data ,b'se its high available solution.

Is Rac also protect the data , and brings database up whenever database goes down?

if not what is meaning of high availability?


please clarify my doubt.

Thanks in advance.

Rampa.

[Tim...]

Hi.

In RAC there is only one database, serviced by instances on several hosts. If one node goes down, only the instance on that node is lost, but the database is still available on the other nodes. Remember, one database on several instances/nodes. In this way, RAC makes a system tolerant of individual nodes failing. This is why it is a high availability solution.

In some cases, a node eviction will cause a node to reboot. If the issue is no longer present, the instance will automatically restart and join the database cluster.

Be careful not to confuse instances an databases. They are not the same thing.

Cheers

Tim...

[adda.road@yahoo.com]

Hi Tim,

Thank You so much for reply.

I am o.k with your answer.

But my question is what happens if the database goes down in case of Rac.

Thanks in advance.

Rampa

[Tim...]

Hi.

For the database to go down it would mean that all RAC nodes were unavailable. In the case of a 4 node RAC, the database would only be down if all 4 servers were off. If any of the 4 RAC nodes were available, the database would be available too.

Cheers

Tim...

[adda.road@yahoo.com]

Hi Tim,

Thanks for reply.
now i got it.

thanks a lot.

Rampa

[Tim...]