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difference between dataguard and replication in oracle??

what is the difference between dataguard and replication in oracle??

are replication and streams one and the same??

any difference between dataguard and golden gate technolgy??

as I see they are all for HA.
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ramavenkatesa
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ramavenkatesa
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3 Solutions
 
logictankCommented:
Oracle Data Guard is primarily for high availability, data protection, and disaster recovery.  An Oracle Data Guard Standby instance provides transactionally consistent copies of the production database, in the event of an unplanned outage or instance maintenance the Data Guard Primary Role Standby Role can be switched so the Standby instance can provide Production services.
Oracle Advanced Replication and Oracle Streams are Oracle's solution for replicating data and internal structures to remote databases.  Advanced Replication is primarily trigger based where Streams is a rule/handler based replication process and considerably more efficient and less error prone than Advanced Replication.
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ramavenkatesaAuthor Commented:
Oracle Advanced Replication and Oracle Streams are Oracle's solution for replicating data and internal structures to remote databases. -----??

Is that not for HA? do we do real time replication? i.e copy the data from server A to server B.

  Advanced Replication is primarily trigger based  -->

can u please share an example or process how this done??

 Streams is a rule/handler based replication process


can u please share an example or process how this done??
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raju1105Commented:
Hi,

Dataguard is for maintaining a standby database for your production database. Your production database archives will get updated to the Standby database to keep in sync and you can switch over /failover to the standby database and make it production database any time.

Where as Golden Gate technology is a third party technology which i guess will replicate at table levels, mean will keep updating the tables and chages done to other objects.

Where as Replication will only create snapshot of the database and some technologies will also update or sync afterwards the replication.
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logictankCommented:
Oracle has specific products for HA and Disaster Recovery, these being Oracle Real Application Clusters (RAC) and Data Guard.  Oracle Advanced Replication and Oracle Streams could be used as a "Sudo" HA environment but there are many disadvantages:
- Replication is not instantaneous
- Update collisions may occur
- Tables without Primary Keys are not good candidates for replication
- No continuous availability if a failure occurs, RAC solves this problem
- Application Failover usually has to be done manually

You can find Advanced Replication information here:
http://www.dba-oracle.com/art_dbazine_mm_repl.htm

You can find a Streams information here:
http://www.dba-oracle.com/t_streams_replication_propagation.htm
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ramavenkatesaAuthor Commented:
active data guard license shd be bought separately from EE edition.
is it so for using streams or advanced replication??

if there are so many disadvantages for replication , why do people use that ?
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raju1105Commented:
Hi,

You dont require a seperate licence to use the dataguard, however it is required only if you plan to use active dataguard in 11g.

However, you will have to cross check with oracle for the normal oracle licences for the oracle software.

Firstly, you will need to decide on what kind of disaster recovery solutions suit your environment and also they are cost based decisions for each solution. If you just need a standby database then oracle Dataguard is very simple solution.

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logictankCommented:
There are many implimentations and benefits for using Advanced Replication and Streams, some of which are:
- Synchronization of data to remote geographical locations
- Propogating information (Sales Order, Customer Info, etc.) from one system to another
- Application Localization (Instead of connecting the application to a remote database, replicate the data to a local instance and connect the application locally)
- Application Availability
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slightwv (䄆 Netminder) Commented:
I'd like to repeat the general thoughts here:  The 'best' approach depends on your specific requirements.

To further add to the confusion:

I personally feel dataguard is a waste of good hardware since you have pretty limited use of the 'standby' database.  I think 'readonly' status is a little better in 11g but it's still readonly.  Now, if you already have RAC and have more than enough hardware you can afford to have a seperate machine sitting there on idle, then dataguard is probably for you.

Prior to 11g, we used Asymmetric Multi-Master Advanced Replication (I know that's a mouthful) and I COULDN'T WAIT until I could get to Streams.  But, my specific requirements allows me to take advantage of replication for a HA solution.

Depending on how your apps work and how you can scale them, replication may or may not work because of the conflict handlers mentioned above.  I was constantly resolving conflicts using Advanced Replication since it is row-based.  Streams helps solve this by looking at changed columns, not the entire row.

That said, I believe my HA using streams is better than Dataguard.  Dataguard 'syncs' at log switches.  On my system these happend every 10-15 minutes.  Using streams it's very rare that I can insert on databaseA, click over to a sql prompt on databaseB and not see the row replicated.  i.e./ it typically replicates the row in under 1 second.

I have my tnsnames set up to try connecting to databaseA first.  if that fails, it then trys databaseB.  No manual cutover just a small delay in connecting while the first attempt times out.


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ramavenkatesaAuthor Commented:
are both physical stand by and logical stand by used as HA solution ??
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slightwv (䄆 Netminder) Commented:
They could be part of a HA solution.
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