AWS DMS Migration Checklist: Cut Over Databases with Confidence
A practical AWS Database Migration Service checklist covering assessment, replication setup, validation, cutover, and rollback for production databases.
Why database cutovers make or break migrations
Applications can often move behind feature flags. Databases rarely can. AWS Database Migration Service (DMS) helps replicate and cut over engines such as MySQL, PostgreSQL, SQL Server, and Oracle — but success depends on preparation, validation, and a rehearsed rollback. This checklist is what our migration teams walk through with US and India stakeholders before production cutover.
Before you enable replication
Confirm source and target engine versions, character sets, extensions, and unsupported features. Capture schema differences early; DMS moves data efficiently but is not a substitute for deliberate schema design on Amazon RDS or Aurora.
Measure change rate (CDC volume), peak transactions, and network path between source and AWS. Undersized replication instances or congested VPN/Direct Connect links show up as lag at the worst moment — cutover night.
Define RPO/RTO with the business. “Near zero downtime” is a design choice that needs continuous replication, validated lag thresholds, and a freeze window for final sync — not a slogan on a slide.
Replication setup and hardening
Create a dedicated DMS replication instance sized for peak CDC. Use separate tasks per logical workload when failure isolation matters. Enable CloudWatch monitoring for CDCLatencySource and CDCLatencyTarget, and alert before lag breaches your cutover criteria.
Lock down security: least-privilege database users, Secrets Manager for credentials, encryption in transit, and tight security groups. Document access for auditors when healthcare or fintech workloads are in scope — without inventing compliance certifications you do not hold.
Validation you should not skip
Row row counts, checksum samples, and critical business queries on source versus target. Involve application owners in a read-only soak against the target. Rehearse cutover in a lower environment with production-like change rates whenever possible.
Prepare application connection string changes, DNS or secret updates, and a communication plan. Parallel-run windows reduce surprise when ORMs or reporting jobs behave differently on the target engine.
Cutover and rollback
Enter cutover only when lag is within threshold, validation sign-off is recorded, and the rollback owner is on the bridge. Stop writers on the source (or briefly quiesce), let DMS flush, promote/cut readers and writers to the target, then monitor error rates and replica lag for dependent systems.
Rollback means restoring write traffic to the source with a clear data divergence policy — which is why cutover timing and freeze discipline matter. After success, rightsize the target and fold the database into your FinOps baseline so migration does not inflate AWS cost.
Get help on the hard parts
If you want a partner-led wave plan, DMS task design, and cutover bridge support, start with our AWS migration services and a free assessment. Pair database moves with cost optimization so the target lands rightsized.
FAQ
Can DMS handle zero-downtime cutovers?
For many workloads, continuous replication plus a short write freeze can achieve near-zero downtime. Exact downtime depends on lag, validation needs, and application cutover steps.
Does DMS replace schema conversion?
No. Heterogeneous migrations often need AWS SCT or manual schema work. Plan schema readiness before relying on DMS for data movement.
Ready for a free assessment?
Talk to our US and India AWS consultants about migration, cost optimization, or DevOps.