Hi,
Although I am not frequently doing this kind of analysis, please try t/code DB02 or DB02OLD.
Every BW persistent object is assigned to a Data Class. This Data Class is in turn assigned to a Table Space (depending on the Database). E.g. for Oracle these tables are TAORA and IAORA if I am correct.
You can also have a look at the following excellent blog series House Keeping / Performance Tuning Activities in SAP BW Systems -- PART 1. The topic Space is discussed in Part 1 and PSA deletion in one of the next parts.
Best regards,
Sander