Saturday, September 10, 2016

RDBMS - Active-Active Data Center from Oracle perspective

Yesterday a question asked to be, actually it was a request to give na Oracle solution for a Active-Active datacenter deployment.
The answer that I gave was via the Oracle presentation, which is available through the following link: http://www.oracle.com/us/products/database/300460-132393.pdf ("Deploying Active-Active Data Centers Using Oracle Database Solutions")

So, basically, there are 4 options we offer for having an active active database deployment.
It actually depends on what we understand by the word Active-Active
That is If we want read+write on DR site,
There are 3 options;

1) Rac Extended Clusters: It is applicable when the distance between the sites is not more than 25 km. This is a RAC configuration in which the nodes can be in different sites.
2) Oracle Streams : This is like a replication, but a double-sided one. No distance limit.
3) Goldengate: Primary and DR are both read-write.  No distance limit.

But, if we want to have a sync copy database and want to use that sync copy database for  only the data extract, reporting and heavy sql queries, in other words, if we want only read; than the option is Active DataGuard.

4) Active Dataguard: After performing the network requirements , the latency between  sites can be decreased to a minimum using a sync trasnport+ real time apply configuration.
However, there won't be any writes taking place in DR, even if the Active Dataguard is implemented.
This is actually for offloading the reports, sql queries and data extract jobs to DR. In case of a disaster, the swiching is almost transparent to the Applications. Not: Active Dataguard requires license.

What about the applications? Well it depends on the applications. Normally, rsync or any storage level technology is enough for having a sync copy of applications. Any configuration that can be done in the application layer can be implemented as well to support a transparent Disaster recovery solution. However, if an active-active data center deployment that needs to be done, the application layer should be analyzed and certified for the active-active data center deployment in place.  This is not an issue when you use Rac Extended Clusters, but when you use golden gate or streams for having active-active datacenter deployment, then the applications should be analyzed and tested accordingly. (even there can be some custom solutions needed there.)

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