DBS-C01 Deployment and Migration Practice Question
A company is using AWS Database Migration Service (AWS DMS) to migrate a 5 TB MySQL database to Amazon RDS for MySQL. The migration is taking longer than expected. The company notices that the source database has a high volume of write operations. Which configuration change would MOST likely improve the migration performance?
⚠ Common exam trap
Candidates often confuse increasing parallelism with enabling Multi-AZ or changing LOB settings, mistakenly thinking these options directly speed up migration, when in fact they address availability or data type handling, not throughput under heavy write load.
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 number of parallel threads in the DMS task settings.
Increasing the number of parallel threads in the DMS task settings allows AWS DMS to process multiple table partitions or row changes concurrently, which directly addresses the bottleneck caused by a high volume of write operations on the source. By default, DMS uses a single thread per table, but when the source is under heavy write load, parallel threads can capture and apply changes more efficiently, reducing the overall migration time.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Increase the number of parallel threads in the DMS task settings.
Why this is correct
Parallel threads allow concurrent loading of data, improving throughput for high-write workloads.
- ✗
Enable Multi-AZ on the target RDS instance.
Why it's wrong here
Multi-AZ provides high availability, not performance improvement during migration.
- ✗
Use a smaller instance class for the replication instance to reduce cost.
Why it's wrong here
A smaller instance class may reduce performance, not improve it.
- ✗
Set the LOB mode to 'Full LOB mode'.
Why it's wrong here
Setting LOB mode to 'Full LOB mode' forces AWS DMS to load all LOB data into memory for every row, which increases per-row processing overhead and exacerbates performance issues when the source already has a high volume of write operations. This option is tempting because Full LOB mode is the correct choice when migrating tables containing large objects that must be fully materialised to avoid truncation, but here the bottleneck is write-heavy transactional load, not LOB handling.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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