Hi Sudha,
If you are loading any of the transaction data then it is required to have master data loaded for that first. This will help to have attributes value generated correctly. Also it helps to in load performance as SID's are already generated.
If you know if any routine is written then where lookup is done in master data to populate any value. If you are able to write any program then you can find it faster.
So better load all Master data first and then start with transactional data.
Regards,
Ganesh