What's changed: Created Professional Cloud Database Engineer Chapter 3 (Domain 3 "Migrate": strategy and planning = zero/near-zero downtime (continuous replication)/extended outage/fallback/DDL-DML conversion/reverse replication; tools and replication = Database Migration Service/Datastream (CDC)/Storage Transfer Service/Transfer Appliance/validation).
3.2Migration tools and replication
Understand choosing migration tools by scenario (Database Migration Service, Datastream, Storage Transfer Service, Transfer Appliance), migrating externally hosted databases, change data capture (CDC) replication, and validating migrations.
Once the strategy is set, choose the tool that fits the scenario—by DB type, acceptable downtime, data volume, and whether continuous changes occur.
3.2.1Choosing migration tools
| Tool | Use |
|---|---|
| Database Migration Service | Minimal-downtime DB migration (homogeneous, some heterogeneous) |
| Datastream | CDC streaming of continuous changes |
| Storage Transfer Service | Transfer large data over the network |
| Transfer Appliance | Physical shipping for huge data on thin networks |
For minimal-downtime DB migration, Database Migration Service; to stream continuous changes via CDC, Datastream—externally hosted databases are also in scope. For bulk transfer, choose Storage Transfer Service (over network) or Transfer Appliance (physical) by requirements. After migration, confirm correctness with validation (row counts, consistency, sample comparison). Map "minimal-downtime DB migration = Database Migration Service" and "continuous change = Datastream (CDC)."
Common: scenario → tool. E.g., "minimal-downtime DB migration" = Database Migration Service; "replicate continuous changes" = Datastream (CDC); "transfer bulk data online" = Storage Transfer Service; "huge data on a thin network" = Transfer Appliance; "confirm post-migration correctness" = validation (counts/consistency).
Watch the mix-ups: (1) Do not confuse Database Migration Service (DB migration), Datastream (CDC replication), and Storage Transfer/Transfer Appliance (file/object transfer). (2) Choose online (Storage Transfer) vs physical (Transfer Appliance) by bandwidth and deadline. (3) Close out migration with validation.
3.2.2Section summary
- DB migration = Database Migration Service; continuous-change replication = Datastream (CDC)
- Bulk transfer = Storage Transfer Service (online)/Transfer Appliance (physical)
- Confirm correctness with row-count/consistency validation after migration
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Quick check
(just a quick review)Q1. To migrate a database to Google Cloud with minimal downtime, which tool is best?
Q2. To stream-replicate continuous source-DB changes via CDC, which is best?
Q3. To migrate hundreds of TB with limited network bandwidth, which is best?
Q4. After migration completes, what should you first confirm?
Q5. To transfer large objects/files into Cloud Storage over the network, which is best?
Q6. Which correctly contrasts Database Migration Service and Datastream?