Any Idea about Tcode OOOS

I want to try transaction OOOS . How actually does it works?

I have a entry like this

PA20 PD10 S RHRHAZ00 PA-REPORT-START_SKIP

What is PD10 where I can find this request code.

I'm not sure what you're asking but if you want the user menu path that will give you the same report:

HR -> OM -> Tools -> Database -> RE_RHRHAZ00 - Display DB records

and

Check out OSS note 87867 for some info related to OOOS.