According to the PMBOK® Guide, specifically within the Direct and Manage Project Work and Monitor and Control Project Work processes, change requests are categorized into four types: corrective action, preventive action, defect repair, and updates.

A preventive action is an intentional activity that ensures the future performance of the project work is aligned with the project management plan.

Focus on the Future: Unlike corrective action, which deals with something that has already gone wrong, preventive action is proactive.

Risk Reduction: Its primary purpose is to reduce the probability of negative consequences associated with project risks before those risks materialize into actual issues.

Examples: Examples include cross-training a team member to avoid a single point of failure or performing extra maintenance on a piece of equipment to prevent a future breakdown.

B. Risk management: This is the overarching knowledge area and set of processes (Identify, Analyze, Plan Responses). While the goal of risk management is to reduce probability/impact, " Risk management " is the framework, whereas " Preventive action " is the specific physical or procedural activity taken to achieve that reduction.

C. Corrective action: This is an intentional activity that realigns the performance of the project work with the project management plan. It is reactive, meaning it is taken after a variance has occurred or a risk has already triggered an issue.

D. Defect repair: This is an intentional activity to modify a nonconforming product or product component. It focuses on fixing a specific deliverable that does not meet quality requirements, rather than addressing the probability of future risk events.

In the PMI framework, both preventive and corrective actions are usually processed as formal Change Requests. They are evaluated through the Perform Integrated Change Control process to ensure that the cost or time required to implement the preventive action is justified by the reduction in risk.