is there any difference between setting up 11gR2 RAC + Dataguard in Active/Active mode Vs 11gR2 + DG + Golden Gate in 11i environment? Besides, are there any pros and cons in setting up one over another?
So you are trying to compare "Real-time Access to Real-time Information" to "Active Data Guard" ?
If yes my knee jerk is check the costs and pick one.
What I like about Active Data Guard is most databases have a large group of "Reader" users.
With Active Data Guard your DR site isn't just sitting there, it can take load off the primary database.
So with Active Data Guard you get two things, DR and a Reader database.
the issue is the business wants to do more that just open up the database for read only. The primary will serve the r/w and secondary will provide access to all changes to the environment. Once complete, switch over.
what are the limitations of using 11gR2 in a/a setup? what is GG adding which 11gr2 a/a is not able to do?
Data Guard with Physical Standby & Real-Time Query (Active Data Guard) is for Disaster Protection in the first place. Additionally, you can use the Standby for Reporting (Read-Only)
Golden Gate or Streams is for Replication in the first place. You could do much more than just read-only reports. You don't need to replicate everything. You could do Multimaster-Replication. Additionally, you get some protection against damage of the source database(s).
The question is: Do you want Disaster Protection or Replication as the most important Business Requirement.
Goldengate is more of a real time replication solution versus Data Guard which is a disaster recovery solution.
If you have many data warehouse applications then it makes sense to implement Goldengate to have real time solution for reporting.