Synchronization
Apply changes to a target schema with pre-flight checks, a transaction and a rollback point.
Synchronization applies a migration to the target. It is the only operation in SchemaSync that writes, and it is built so that every step before the write is reversible and every failure is recoverable.
Synchronize orders_dev → orders_prod
Step 3 of 4 · applying changes
Pre-flight checks
Privileges, engine and charset verified
Backup target schema
orders_prod-20260714-2104.sql · 42 MB
ALTER TABLE `orders`
MODIFY COLUMN `status` — running
CREATE INDEX `idx_orders_placed_at`
Queued
Verify and re-compare
Confirms the target matches the source
What happens, in order
Pre-flight checks
Privileges are verified for every statement in the plan, and engine, character set and version compatibility are confirmed. Problems are reported before anything runs, not halfway through.
Backup
The target schema is backed up automatically. This is on by default and we recommend leaving it that way.
Rollback point
A restore point is recorded so the pre-migration state can be recovered even if the transaction cannot be used.
Apply, as one transaction
Statements run inside a single transaction. A failure at any point rolls the target back to where it started.
Verify
SchemaSync re-compares both schemas afterwards and confirms the target now matches the source.
Applying only part of a comparison
Clear the checkbox on any difference you are not ready to deploy. The generated plan contains only what remains selected, with dependency order recalculated — so shipping one change and holding another back does not mean hand-editing SQL.
Large tables
An ALTER TABLE on a large table can hold locks for a long time. Generate the script rather than applying it directly, then run it in your maintenance window or feed it to a tool such as pt-online-schema-change. Estimated impact is shown next to each statement in the plan.