On Oracle 11.2.0.4 , mixed environment OLTP,OLAP databases.

i) We want to do an estimation about how much space can be reclaimed in database and in backup by using advanced compression?

ii) Also how to find tables good candidate for using advanced compression?

iii) cautions/limitation for advanced compression?

any suggestion for how to do a POC on advanced copression feature, to show benefit to management?

I think the space saved should be costlier than advanced compression license, then only it makes sense to but the feature.

So, may not be suitable for handful of databases, rather than enterprise wide implementation seems to make sense, what say?