4.2 Migration Approach
Database Migration
AWS Database Migration Service (DMS)
- Function: Migrates data from Source to Target DB.
- Continuous Replication: CDC (Change Data Capture) replicates ongoing changes for minimal downtime.
- Schema Conversion Tool (SCT): Converts schema (tables, views, stored procedures) from Heterogeneous sources (Oracle → PostgreSQL). DMS moves data; SCT moves schema.
WARNING
Exam Gotcha: DMS does not automatically migrate Secondary Indexes, Stored Procedures, or Triggers. You must use SCT (Schema Conversion Tool) to handle schema conversion first.
Server Migration
AWS Application Migration Service (MGN)
- Replacement: Replaces the older Server Migration Service (SMS).
- Mechanism: Uses block-level replication agent.
- Cutover: Launches EC2 instances from the replicated data. Short downtime.
Data Transfer
AWS DataSync
- Function: Online data transfer. Agents on-prem → S3/EFS/FSx.
- Protocol: Proprietary, WAN-optimized. Faster than CLI/rsync.
- Use Case: Ongoing replication or large active migrations.
AWS Snow Family (Cheatsheet)
| Device | Capacity (Usable) | Use Case |
|---|---|---|
| Snowcone | 8 TB / 14 TB (SSD) | Portable, Rugged, Edge computing. IoT. |
| Snowball Edge | 80 TB (Storage) / 42 TB | Data Center migration. Compute on board. |
| Snowmobile | 100 PB | Exabyte-scale migration (Truck). |
WARNING
Exam Gotcha: Use Snow Family when network bandwidth is insufficient (e.g., would take weeks/months to upload). Use DataSync if you have a decent pipe (Direct Connect) and need active sync.