If you are using DPA then you might want to check the "Data Collection Reference Guide" for DPA

Can you please help me with a link?

regular folder or an mtree ?

sure! I didn't the version you have. Below is for 6.2

https://support.emc.com/docu56640_Data-Protection-Advisor-6.2-Data-Collection-Reference-Guide.pdf?language=en_US

So, why not use dir command? (for app/OS guys)

we are protecting some legacy applications because they are not supported by any product, so dumping native backups to DD CIFS directly

the OS /APP guys are finding it difficult to report how much they have actually dumped

Well, the dedupe ratios etc are also required by our team as well.

the incremental cannot be identified with dir command

Shouldn't size of dump or date (if you use some scheduler) tell you (cross-reference) which level it is?

Knowing how much it is on DD might be tricky at file level.  With backup application I can get that info easy, but working directly I really don't know as I have no such experience.

I checked the logs etc, which is easy to pull from a unix client using scripting

but on windows which dump data to cifs, the dba or windows guys are facing problem

and

customers want reports from DPA which they are habituated since long, so unable to find a correct method

If you know in which file (log) this is when using UNIX, it should be easy for Windows as well (use powershell).  I still have no idea in which log that would be on DD - which log are you referring to?

As for DPA, I doubt they can pull this per file unless API provides this data and most importantly this data is stored on DD.