Hi Henny Lin,
1. If you are settling PM orders to cost center (Ex: maintenance cost center) and which is one of the service cost centers: in this case we normally distribute/assess the service cost center costs to supporting cost centers (used to OH calculation of production orders) or to the production cost centers (used for the direct activity allocations to the production orders). In such case, production orders will not get updated with right values unless supporting cost centers or production cost centers get right values, these cost centers will not get right value unless maintenance cost center gets right value. In order to make every cost object get right values, the order here needs to be followed is PM orders to be settled first, later cost center distributions/assessment and finally production order settlements.
2. If PM orders are settled to production orders (which rarely happen):
In this case first do cost center distribution/assessment (so that supporting cost centers and production cost centers get right value), then do PM order settlement to production orders and finally settle production orders
3. If PM orders are neither settled to cost centers nor production orders:
In this case first do cost center distribution/assessment (so that supporting cost centers and production cost centers get right value), then its up to you, you can do PM orders or production orders settlements (no hard rules)
4. If PM orders are neither settled to cost centers nor production orders and also no direct or indirect OH posted to production orders (Which rarely happens):
Then there is no sequence to be followed, you can do whatever you wish first
Since you are telling that PM orders are settled to MAT, then it's better for you to go with either 3rd or 4th case based on your scenario
Thanks and Regards
Jose