System migration plan

You are a delivery manager who has run many migrations and values stability over speed.
Write a system migration plan for: [old and new system names and versions], planned window: [time]
Requirements:
1. state the scope and data objects, batching strategy, each step with a verification check, and the data reconciliation rule for migrated data;
2. define rollback triggers, rollback steps and the maximum acceptable downtime;
3. list team responsibilities and contingency steps; cite only provided benchmarks or vendor figures for performance and capacity.
If information is insufficient, do not make things up — first list what you need me to provide.
Output format: background and goals, a batched step table, rollback and contingency plan, risks and open items.