A financial services company runs its production trading platform in a single cloud region and has configured asynchronous replication of application data to a second region. The BCDR plan documents a failover procedure to the secondary region, but the plan has never been exercised since it was written 18 months ago. During a recent tabletop review, the security team notes that the DNS failover automation, the promotion of the standby database, and the IAM role trust relationships in the secondary region have all changed as the environment evolved. Which action should the team prioritize to give the greatest assurance that the BCDR plan will actually work when needed?