A strange situation about DSI module

Dears,

After build synchronization project for DSI and do an initial synchronization. I create an account definition and assign it to an employee.

Then I assign the DB role which is synchronized from DB by synchronization project to employee, the provisioning process correctly assign the DB role to the employee.

I remove the DB role from the employee, the provisioning process also delete the DB role from the employee.

So, Add and Remove is both OK, but, a strange situation happen, when I remove the account definition from the employee, the DB role is not shown on the Manager hyperview, 

it still exist in Database. I don't know why the DB role not deleted from the employee in Database, could you help me, very thanks~~

Thanks

David