I currently have an existing PostgreSQL 12 instance running on Google Cloud Platform with several databases containing critical data. Now, I need to migrate additional data from a PostgreSQL 9.6 instance to the existing PostgreSQL 12 instance without affecting the databases already present in the PostgreSQL 12 instance.
Specifically, here are the key points:
The PostgreSQL 12 instance already contains several databases with important data that I must preserve. I want to migrate data from the PostgreSQL 9.6 instance, the entire cluster, to the PostgreSQL 12 instance, ensuring that the existing databases in the PostgreSQL 12 instance remain intact and unaffected by the migration process.
I've reviewed the documentation for Google Cloud's Database Migration Service (DMS), but I'm unsure about how to proceed with the migration process while ensuring the integrity of the existing databases in the PostgreSQL 12 instance. From what I read I understood that the migration job will create a replica on the existing 12 one, my main doubt is what will happen once that this replica is promoted. It will replace the data I previously had on the 12? Using DMS is the best strategy on my case?