Hi Ashish,
From an end users perspective, SAP is having a standard report S_AHR_610160509 for Vacant Position.
This you will find in Easy Access Menu itself.
HR -- OM -- Info Systems -- Position -- S_AHR_610160509 (Vacant Position).
From little technical side you may use table HRP1007 for Planned Version 01 and Object Type S in T-Code: SE16
Regards
Siva