You plan to use Database Migration Service to migrate data from a PostgreSQL on-premises instance to Cloud SQL. You need to identify the prerequisites for creating and automating the task. What should you do? (Choose two.)

Database Migration Service (DMS) for PostgreSQL relies on logical replication to perform continuous, minimal-downtime migrations. For this mechanism to function correctly with an on-premises source, two key prerequisites must be met. First, the pglogical extension must be installed on the source database. DMS uses this extension to capture and stream data changes to the Cloud SQL destination. Second, every table intended for migration must have a primary key. Logical replication requires a primary key to uniquely identify rows for replicating UPDATE and DELETE operations accurately. Tables lacking a primary key will not be migrated by DMS.

A. Drop or disable all users except database administration users. This is not a DMS prerequisite. DMS only requires a specific user with sufficient replication privileges; other application users can remain active.
B. Disable all foreign key constraints on the source PostgreSQL database. This is incorrect and would compromise data integrity on the source. DMS is designed to handle data with existing constraints.
D. Shut down the database before the Data Migration Service task is started. This is incorrect. DMS is designed for minimal-downtime migrations and requires the source database to be online to capture ongoing changes (CDC).

1. Google Cloud Documentation: Prepare a source PostgreSQL database.

Under the "Prerequisites" section, it explicitly states: "Install the pglogical extension on your source database... Database Migration Service uses the pglogical extension to connect to the source database and stream changes to the Cloud SQL destination database." This supports option E.

The same section also states: "All tables in the database that you want to migrate must have a primary key." This supports option C.

2. Google Cloud Documentation: Known limitations | Database Migration Service.

Under the "General limitations" section, it lists: "Tables without a primary key aren't migrated." This further validates option C as a critical prerequisite.