Changing a database is not just copying tables. You need to design a transition where old and new structures live together for a while, errors can be rolled back, and user transactions are never lost.
First extract the data contract
Do not start moving before field types, required values, unique keys and relationships are documented. A field that looks “nullable” in the old system can stop a workflow in the new one.
Safe migration steps
- Build the new structure without breaking the old system.
- Take the first copy and verify numerically.
- Track new records with dual writes or a change log.
- Open read traffic on the new system in a controlled way.
- Compare differences, then switch the write source.
- Decide rollback time and conditions in advance.
Success is not “we moved it”
Real success is record counts matching, relationships preserved, critical reports giving the same results, and users completing their work uninterrupted.
No migration without a rollback plan
Shutting the old system down right after the new one opens can be tempting. But without an observation period, accessible backups and a rollback procedure, that decision grows the risk.
Source / further readingWYN — Long-term system approachThis article does not copy the original content of the source; it is WYN’s practical interpretation. For current headlines, check the publication date and the source page separately.