We're having two masters on 11g and then four on 5.2. We would be enabling Referential Integrity on 11g, however the below link recommends that we should "enable" on all masters. What are downside of not enabling on other 5.2 masters? Do anyone has strong suggestion to put in.
There is no hard limit on masters in DS5.2, but testing showed that there was the possibility of fairly severe performance issues with too many masters.
The more masters you have, and the longer you run with >4 masters, the more likely you are to run into performance issues. No guarantee that you will, its just a possibility.
The biggest downside is that configurations with > 4 masters are not supported, so any issues and you call Oracle for support, they may just tell you its an unsupported configuration.