DBS-C01 Deployment and Migration Practice Question
A company is migrating a 3 TB PostgreSQL database from on-premises to Amazon RDS for PostgreSQL. The migration must have minimal downtime. The on-premises network bandwidth to AWS is 1 Gbps. The database supports a critical application that cannot be stopped for more than 30 minutes. The migration team has set up AWS DMS with ongoing replication using CDC. The initial full load is expected to take 8 hours. During the migration, the DMS task fails with an error indicating that the source database's transaction log is being cleaned before DMS can capture changes. The source database has a transaction log retention period of 24 hours. The migration team notices that the CDC phase falls behind during peak hours. What should the team do to complete the migration successfully within the downtime window?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Increase the transaction log retention period on the source database and use a larger DMS replication instance
The issue is that DMS cannot keep up with changes during peak hours, causing the transaction logs to be cleaned before DMS reads them. Increasing the source database's transaction log retention period gives DMS more time to catch up. Using a larger DMS replication instance will increase processing capacity. Option C is the best combination. Option A (Snowball) would take too long. Option B (Direct Connect) doesn't solve the log retention issue. Option D (decrease retention) makes the problem worse.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use AWS Snowball to transfer the full database and then use DMS for CDC
Why it's wrong here
Snowball transfer would take days, exceeding the downtime window.
- ✗
Increase the network bandwidth using AWS Direct Connect
Why it's wrong here
Network bandwidth is not the bottleneck; DMS processing capacity is.
- ✓
Increase the transaction log retention period on the source database and use a larger DMS replication instance
Why this is correct
Longer log retention prevents cleanup before DMS captures changes; larger instance boosts CDC throughput.
- ✗
Decrease the transaction log retention period to free up space
Why it's wrong here
Decreasing retention would exacerbate the problem.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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