"Do we have any changes ... for PlSql developers(OLAP environment)"

Not really. That is one of the goals of Exadata - that whatever you have done in the past, continues to work in the same way or better.

You're right that most of the *internals* concerns DBA's but there are benefits for the developer in having a knowledge of those parts of Exadata that pertain to running queries faster, especially analytical or OLAP style queries.

The book below is more of a DBA's resource

http://www.apress.com/us/book/9781430262411

but still there is some great content there in the first couple of hundred pages on the elements that concern developers most, namely, getting the most out of Exadata from a query performance perspective. It provides mainly a good understanding of perhaps re-framing your mindset in terms of getting good performance from queries, namely, its not *always* about indexes.