Hi,
.We have position object as a parent and employee is the child object, both of them having the master-detail relationship, we have no. of records in our system for child object. Now our business requirement comes that we have to change MDR to Lookup relationship. So what are the considerations you have to keep in mind while changing it.
 
one consideration I know is if there is any rollup on master  first remove it . 
 Now  suppose there is a roll-up summary in between them and we have lots of data and we don't want to lose data then how can you achieve this.