Database migration is far more complex than server migration. Servers share a common language (OS and file systems), but DB engines each have different SQL dialects, data types, built-in functions, and procedural languages. Oracle's PL/SQL, SQL Server's T-SQL, and PostgreSQL's PL/pgSQL look syntactically similar but have dozens of incompatible functions and data types.
AWS DMS (Database Migration Service) manages this complexity. CDC (Change Data Capture) tracks changes in real-time while the source DB continues operating, and SCT (Schema Conversion Tool) enables automatic schema and code conversion between heterogeneous engines