Your system will define who has these responsibilities. A process or system is considered effective when it meets its objectives. This highlights again the importance of process and system objectives being documented. The process is under control when it can be relied upon to meet its objectives. This suggests that the process of setting objectives for key processes is itself a key process.
Preventive action is widely misunderstood.
A graphic story to illustrate the problem is the one about bananas. Someone slips on a banana skin left on the floor. Only corrective action is possible to prevent recurrence . Preventive action prevents the occurrence of nonconformances, defects, accidents and pollution. This suggests that the primary responsibility for preventive action remains with executive management unless, of course, the team has been empowered to make such investments.