Hi Prasenjit ,
In its ability to handle large volumes of data Powerpivot does resemble Access , but this is a very superficial resemblance.
In reality they are vastly different.
Access is a database management system , which can store data , and process it in all the different ways that any DBMS can , though not necessarily to the same extent ; obviously Access cannot be compared to Oracle.
Powerpivot handles data the way Excel pivot tables do , but in a vastly superior way , so that the data processing power of Powerpivot is orders of magnitude higher than that of Excel pivot tables.
As far as analysts are concerned , they now have a business intelligence tool which earlier required an IT specialist to manage. Querying database tables with all their complex relationships required an SQL programmer ; with Powerpivot , you can achieve almost as much , without needing any knowledge of SQL.
See the following links for more in-depth information :
https://www.linkedin.com/today/post/article/20141105095015-27895769-why-is-powerpivot-important
http://sqlmag.com/blog/does-excel-power-pivot-replace-data-warehouse
http://www.pcworld.com/article/205260/how_microsoft_powerpivot_will_disrupt_bi.html
http://ebs.dk/en-US/aboutbi/Pages/PowerPivot-isitgood.aspx
Narayan