Database Migration Service (DMS) migrates databases to Cloud SQL and AlloyDB. Serverless, free, with minimal downtime through continuous replication.
What is Database Migration Service?
DMS is a fully managed service for homogeneous and heterogeneous database migrations. It continuously replicates data from on-premises, AWS RDS, Azure, or other sources to Google Cloud.
The service is serverless: you don’t need to manage any infrastructure. Replication scales automatically with data volume.
Migration Types
Homogeneous Migration
Same database engine: MySQL to MySQL, PostgreSQL to PostgreSQL.
- No schema mapping required
- Full feature compatibility
- Minimal adjustments
Heterogeneous Migration
Different engines: Oracle to PostgreSQL, SQL Server to PostgreSQL.
- Schema conversion required
- Manual adjustments for stored procedures
- Migration Assessment Tool helps with planning
Migration Process
1. Assessment
├── Analyze source database
├── Check compatibility
└── Create migration plan
2. Schema Migration
├── Convert schema (for heterogeneous)
├── Create target database
└── Deploy schema
3. Data Migration
├── Initial snapshot
├── Start CDC replication
└── Continuous synchronization
4. Cutover
├── Stop application
├── Final synchronization
├── Switch application to target
└── Decommission sourceTypical Use Cases
AWS RDS to Cloud SQL
Migrate from AWS RDS (MySQL/PostgreSQL) to Cloud SQL. DMS replicates continuously, cutover happens with just minutes of downtime.
On-Premises to Cloud
Connect on-premises databases via VPN or Cloud Interconnect. DMS replicates over the encrypted connection to Cloud SQL.
Oracle Exit
Switch from Oracle to PostgreSQL on Cloud SQL or AlloyDB. The Schema Conversion Tool converts DDL; complex PL/SQL requires manual adjustment.
Benefits
- Free: No DMS fees, only target database costs
- Serverless: No infrastructure to manage
- Minimal downtime: Cutover in minutes instead of hours
- Continuous replication: No data loss through CDC
Limitations
- GCP targets only: Migrates only to Cloud SQL and AlloyDB
- Heterogeneous migrations: Require manual adjustments
- Complex procedures: PL/SQL, T-SQL need rewrite
Integration with innFactory
As a Google Cloud Partner, innFactory supports you with database migrations: assessment, schema conversion, cutover planning, and post-migration optimization.
Typical Use Cases
Technical Specifications
Frequently Asked Questions
What is Database Migration Service?
Database Migration Service (DMS) is a serverless service for database migrations to Google Cloud. It continuously replicates data from source to target and enables cutover with minimal downtime (minutes instead of hours).
Which databases are supported?
Supported sources are MySQL, PostgreSQL, SQL Server, and Oracle (with schema conversion). Targets are Cloud SQL (MySQL, PostgreSQL, SQL Server) and AlloyDB (PostgreSQL-compatible).
How much does Database Migration Service cost?
DMS itself is free. You only pay for the target database (Cloud SQL or AlloyDB) and possibly network egress for migrations from on-premises or other clouds. This makes DMS significantly cheaper than third-party tools.
How does migration work technically?
DMS first performs an initial snapshot, then continuously replicates changes via Change Data Capture (CDC). The application remains on the source database. During cutover, replication is stopped and the application switches to Cloud SQL.
Can I migrate Oracle to PostgreSQL?
Yes, but Oracle requires schema conversion since the dialects differ. DMS supports this with Migration Assessment and Schema Conversion Tool. Complex PL/SQL procedures require manual adjustment.
