Exams / SAP-C03 / Study guide / Rehosting and data migration (AWS Transform MGN, DMS, DataSync)
Rehosting and data migration (AWS Transform MGN, DMS, DataSync): SAP-C03 study notes and practice questions
What to know about Rehosting and data migration (AWS Transform MGN, DMS, DataSync) for the SAP-C03 exam, from the Resilience, Migration, and Business Continuity domain (15% of the exam guide), then 1 free question to test it. Part of the SAP-C03 study guide.
These questions ask how to move servers, databases and files to AWS with minimal downtime and the least effort. The constraints are usually the cutover window, the source platform and whether the database engine changes.
Rehosting servers with AWS Transform MGN
AWS Transform MGN (previously AWS Application Migration Service) is the main rehost tool.
Install the replication agent on source servers (physical, VMware, Hyper-V or other clouds). It continuously replicates disks at block level to a low-cost staging area subnet in the target account.
Launch templates and post-launch actions set instance type, subnet, security groups and run scripts (for example, install agents, convert licenses).
Run test launches first, then a cutover launch during the window; the source keeps running until you finalize, so rollback is easy.
Downtime is only the final sync and DNS switch, typically minutes.
AWS Transform adds agentic AI help for large programs, including VMware migrations (discovery, network conversion to VPC constructs, wave planning and execution through Transform MGN) and .NET and mainframe modernization.
Databases with AWS DMS
Need
Use
Same engine, minimal downtime
DMS full load + change data capture (CDC), or native replication tools
Different engine (Oracle to Aurora PostgreSQL)
DMS Schema Conversion or AWS SCT for schema and code, then DMS for data
Variable or unknown migration load
DMS Serverless (capacity scales automatically)
Confirm data matches
DMS data validation
CDC keeps the target in sync until cutover, so downtime is only the switch.
DMS migrates data, not secondary indexes, triggers or stored procedures; conversion tools or native scripts handle those.
Very large homogeneous databases are often faster with native tools (such as backup and restore to RDS, or physical replication) plus DMS CDC for the delta.
Files and bulk data
AWS DataSync copies NFS, SMB, HDFS and object storage to S3, EFS or FSx, with encryption, integrity checks, scheduling and bandwidth limits. It suits one-time migration and recurring sync.
Transfer Family keeps SFTP-based partner flows working against S3 or EFS.
Data Transfer Terminal lets you bring devices to an AWS location and upload large datasets quickly when the network would take too long.
Calculate transfer time: at 1 Gbps, 100 TB takes over 9 days at full utilization, so large datasets plus a short deadline push you to physical transfer or a bigger link.
How to choose
Scenario wording
Pick
“Lift and shift 500 VMs, minimal downtime”
AWS Transform MGN
“Oracle to Aurora PostgreSQL”
DMS Schema Conversion or SCT, then DMS full load + CDC
“Move 200 TB of NFS shares, then keep in sync until cutover”
DataSync
“Partners upload by SFTP; keep that interface”
Transfer Family
“VMware estate, convert networks too”
AWS Transform for VMware
Common traps
Snapshot-and-copy scripts instead of continuous replication.
DMS alone for a heterogeneous migration without schema conversion.
Using the retired name as a reason to rule out the service: Application Migration Service is now AWS Transform MGN.
Full load only when the window allows just minutes of downtime.
Copying files with rsync scripts where DataSync gives validation and scheduling.
A utility company runs about 300 virtual machines on VMware in its data centers, a mix of Windows and Linux. The machines are moved in waves, and each wave must cut over within a four-hour maintenance window with the data current up to the cutover.
The application teams want no changes to the operating systems or applications before the move, and the migration team wants to rehearse each cutover without affecting production.
Which solution meets these requirements?
Choose one answer.
AA. Use AWS Transform MGN (formerly AWS Application Migration Service), install its replication agent on each machine, and run test cutovers before each production cutover in the window.
BB. Use AWS Database Migration Service full-load and change data capture tasks to replicate each application's database to Amazon RDS, and redeploy the applications on new EC2 instances in AWS.
CC. Export each virtual machine as an image file, copy the files to AWS, and import them during the window, so the full data set moves in one step.
DD. Rebuild each machine from a fresh AMI, then move the data across with a file copy tool during the window, applying the application changes as the final step.
Show the answer and explanation
Answer: A
A. Right: Correct. The service replicates each machine's disks continuously, so the cutover needs only a short final sync within the window. Test cutovers let the team rehearse each wave without touching production, and the machines move without operating system or application changes.
B. Wrong: DMS replicates databases, not whole virtual machines, so the application servers would have to be rebuilt on new instances. That changes the operating systems and applications, which the teams ruled out.
C. Wrong: Exporting and importing full images needs the machine stopped for the whole copy, which the four-hour window cannot cover for large machines. The option also gives no way to rehearse the cutover.
D. Wrong: Rebuilding changes the operating systems and applications, which the teams ruled out, and the file copy adds risk and time to every window. This is a re-platform, not a rehost.
Explanation
AWS Transform MGN replicates the running machines continuously, which keeps the final cutover inside a short window and allows rehearsal with test cutovers. DMS moves only databases and forces a rebuild of the servers, while full image exports and rebuilds either exceed the window or change the systems.
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