Hi Hairul
How are you man?
Orginal part master is a list of part number which OEM / Manufacturer supplies to you.
However a lot of times you do not use all the parts which the OEM parts master have, so to avoid creation of surplus part master or active part masters the OMARA table is been provided to just fill in the table will all the OEM part numbers list.
So you do no have active part masters, but if you want to create any part number which is not created as material you just use the tcode /DBM/MMXX to create them quickly & start using them in the DBM order.
Regards,
Sachin Balmiki