To ensure transparency during a critical database migration with multiple vendors, establish clear roles and responsibilities using a RACI matrix. Create a detailed migration plan with milestones, dependencies, and approval gates. Foster open communication through regular meetings, shared platforms like Teams or Slack, and encourage feedback. Use project management tools (e.g., Jira) and dashboards to track progress and share updates. Maintain a centralized document repository for plans, logs, and meeting minutes. Identify risks collaboratively, document contingency plans, and define escalation paths. Provide unified, regular status reports to stakeholders, consolidating vendor updates for a clear view of progress and challenges.

Establish Clear Communication Channels: Set up regular meetings, updates, and a shared project dashboard to track progress. Define Roles and Responsibilities: Clearly outline each vendor’s scope of work, deliverables, and deadlines. Document All Decisions: Keep records of key decisions, issues, and resolutions for accountability. Monitor Progress and Performance: Use tracking tools to ensure timelines and quality standards are being met. Foster Collaborative Problem-Solving: Encourage open discussion to address challenges as they arise. Provide Visibility to Stakeholders: Regularly update internal teams and other stakeholders with progress reports and risk assessments.

I agree with all points suggested here, along with that we now have quick options of instant messaging which should be initiated in advance and keep posting progress on all points as per your SOA. This makes are teams which are involved are aware of the progress and issues if faced any and will also help in quick actions and remedies. Also it's necessary to inform all stakeholders post major milestones are achieved and not just after final completion. This gives the confidence to everyone that they are aware of what is happening and especially when you work in different geographic locations

some vendors may have proprietary communication protocols in app level to gain the maximum performance of the database designed for their application, so it is important to clarify data structures based on involving vendors protocols, communication data documents and software architectures to avoid any conflict during migration process. preparing a data structure mapping from old data structure to the new one helps stakeholders to have more efficient cooperation and communication in transition process.