Vacant Positions in PeopleSoft HRMS PS_POSITION_DATA

Select DISTINCT A.position_nbr From Sysadm.Ps_Position_Data A Where
A.Effdt = (Select Max(A1.Effdt) From Sysadm.Ps_Position_Data A1 Where A.Position_Nbr =A1.Position_Nbr)
And A.Eff_Status = 'A'
And A.Position_Nbr Not In ( Select Distinct Position_Nbr From Sysadm.Ps_Current_Job)) Aa Where Aa.Position_Nbr Not In
(Select distinct position_nbr From Sysadm.Ps_Job Where Effdt Between Sysdate-180 And Sysdate
and position_nbr in (Select position_nbr From Sysadm.Ps_Position_Data A Where
A.Effdt = (Select Max(A1.Effdt) From Sysadm.Ps_Position_Data A1 Where A.Position_Nbr =A1.Position_Nbr)
And A.Eff_Status = 'A'
And A.Position_Nbr Not In ( Select Distinct Position_Nbr From Sysadm.Ps_Current_Job)));