R12912 purge program question

Hi

we need to purge all old fixed asset records that are no longer active.

Can we run R12912 with open data selection (with out specifying specific assets) over few years to purge  all fixed assets that were disposed for last  few years?

I have read document 1470184.2 but it does not give program logic details and says that it will purge only records for the prior year, but we need to run the program for multiple years?

How the program determines that asset was disposed? What is the logic behind it?

Thank you