connection Oracle OLAP , Oracle application server, Oracle BI answer and BI server to MS SQL

Nope, there are few differences in terms of Oracle and SQL Server Architectures..
So, I don't think Oracle DB can be simply replaced or upgraded to SQL Server. You might need to work out on converting the logics and ensure they are working fine in SQL Server.

"So, I don't think Oracle DB can be simply replaced or upgraded to SQL Server."

no. I mean if logic is all in application tier, can we just change connection to SQL server?

assuming all data and schema already replicated to the SQL server.

I also mean all oracle DB level business logic are move to the application level, then just change connection string, right?

Yes, it might but we need to test it completely..

please help to answer this:

https://www.experts-exchange.com/questions/29103116/effort-steps-to-migrate-from-Oracle-10g-to-DB2.html?anchor=a42590641¬ificationFollowed=208551936&anchorAnswerId=42590641#a42590641

Hi marrowyung,
Kindly request you to let me know for more details on this question or else request you to close it accordingly..

ttks.