How to scale down gp3 storage of RDS instance (PostgresSQL) using DMS?

Hello.

It might be easier to do a database dump than to set up a DMS.
https://repost.aws/knowledge-center/rds-db-storage-size

When using DMS, the following documents may be helpful.
https://repost.aws/knowledge-center/dms-migrate-postgresql-to-postgresql

Hi,

You should give a detailled read to this blog post: https://aws.amazon.com/blogs/database/rolling-back-from-a-migration-with-aws-dms/

It explains you how to prepare a database migration move with DMS but also how to have the the right fallback mechanism with minimal failover and no data loss in case your migration goes wrong.

Best,

Didier