A solid data migration plan for upgrading CLM centers on a careful, end-to-end approach that preserves contract data and structure through the upgrade. The best answer reflects the full sequence: plan the migration scripts so you know exactly how each piece of data will move into the new version, test those scripts in a sandbox to catch issues without touching production, migrate the elements that define contracts—templates, clauses, and fields—so the business logic and data capture remain intact, verify the mappings so every old field lines up correctly with its new counterpart, and validate data integrity after the migration to ensure no data is lost, relationships stay intact, and search and reporting function as expected. This comprehensive approach reduces risk, ensures a smooth transition, and preserves the usability of contracts in the new system. Skipping tests, migrating only partial components, or deleting old data without verification would leave gaps, introduce errors, and threaten data reliability.