Lengthy process of importing ReqIF into DOORS Next

We have installed DOORS Next 7.0.3 onto our company servers few days ago. So far the operation is running smoothly except some performance issues particularly related to importing ReqIF file into the database. For example, a 24MB file with approximately 9,000 artifacts took 90 minutes to import. Another 3MB file with around 900 artifacts took about 20 minutes to import. These files only contain a few linkages and some embedded tables within the requirements. Can anyone tell me if this is underperforming? So far I don't experience other performance issue except this importing issue, what might be the reason(s) causing this issue?