Database Migration Service (DMS) migrates databases to Cloud SQL and AlloyDB. Serverless, with significantly reduced 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 Cloud SQL for MySQL, PostgreSQL to Cloud SQL or AlloyDB for PostgreSQL, SQL Server to Cloud SQL for SQL Server.
- No schema mapping required
- Full feature compatibility
- Minimal adjustments
Heterogeneous Migration
Different engines: Oracle or SQL Server to Cloud SQL/AlloyDB for PostgreSQL.
- Schema conversion required
- Manual adjustments for stored procedures
- Migration assessment capabilities help 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, and cutover happens with significantly reduced downtime.
On-Premises to Cloud
Connect on-premises databases via VPN or Cloud Interconnect. DMS replicates over the encrypted connection to Cloud SQL or AlloyDB.
Oracle Exit
Switch from Oracle to PostgreSQL on Cloud SQL or AlloyDB. Schema conversion capabilities convert DDL; complex PL/SQL requires manual adjustment.
Benefits
- Cost-effective: Homogeneous migrations are free; heterogeneous migrations only incur usage-based costs above the free allowance
- Serverless: No infrastructure to manage
- Reduced downtime: Cutover after continuous replication instead of long offline windows
- Continuous replication: No data loss through CDC
Limitations
- GCP targets only: Migrates only to Cloud SQL and AlloyDB
- Heterogeneous migrations: Require manual adjustments and are billed by volume
- Complex procedures: PL/SQL, T-SQL may need partial rewrite
Integration with innFactory
As a certified 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 significantly reduced downtime compared to classic dump-and-load migrations.
Which databases are supported?
Supported sources are MySQL, PostgreSQL, SQL Server, and Oracle (with schema conversion). Targets are Cloud SQL (for MySQL, PostgreSQL, SQL Server) and AlloyDB for PostgreSQL, depending on whether the migration path is homogeneous or heterogeneous.
How much does Database Migration Service cost?
Homogeneous migrations (same database engine on source and target) are free; you only pay for the target database. Heterogeneous migrations (e.g., Oracle or SQL Server to PostgreSQL) are billed by data volume transferred, with a monthly free allowance. Google Cloud's current pricing page is authoritative for exact figures.
How does migration work technically?
DMS first performs an initial snapshot, then continuously replicates changes via Change Data Capture (CDC). The application remains active on the source database throughout. During cutover, replication is finally synchronized and the application switches to the target database.
Can I migrate Oracle to PostgreSQL?
Yes, Oracle can be migrated to Cloud SQL for PostgreSQL or AlloyDB for PostgreSQL. Since this is a heterogeneous migration, schema conversion is required; DMS supports this with migration assessment and schema conversion capabilities. Complex PL/SQL procedures typically require manual adjustment.
Note: All product information on this page has been compiled with care, but is provided without guarantee and may be outdated or incomplete. Cloud services evolve rapidly — features, pricing, SLAs, and availability change frequently. Authoritative and up-to-date information can only be found on the official product page of Google Cloud (official documentation). This page does not represent an offer by Google Cloud.
