Implementing a process in a change management system takes place after:

Rigorous peer review is a valuable step in the design and planning phase of a change, helping to identify potential issues, but it precedes the final approval for implementation.

Consultation with the vendor may be necessary during various stages of a change, especially for external products, but it is not the final gate before implementation in a change management system.

An initial test in a sandbox or test environment is a crucial step for validating the change's functionality and impact, but this testing typically occurs before the CAB gives final approval for production deployment.

The Change Advisory Board (CAB) is responsible for reviewing, evaluating, and approving proposed changes to ensure they are beneficial, properly planned, and do not introduce unacceptable risks. Implementation of a change in a production environment is a direct consequence of the CAB's formal approval, marking it as ready to proceed.