DBS-C01 Management and Operations Practice Question
A database administrator is using AWS DMS to migrate an on-premises Oracle database to Amazon RDS for PostgreSQL. The migration has been running for several hours, but the full load phase is taking much longer than expected. The CPU utilization on the DMS replication instance is consistently below 10%. What is the MOST likely cause of the slow performance?
⚠ Common exam trap
Many exam-takers assume slow migration is due to DMS configuration (like LOB mode or parallelism) or source-side issues, but the low CPU on the replication instance is a key indicator that the bottleneck is on the target side, specifically I/O throttling.
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
✓
The target RDS instance is throttling write operations due to low IOPS.
When the target RDS instance has insufficient IOPS, write operations are throttled, causing a bottleneck that slows down the full load phase. Even though the DMS replication instance's CPU is low (below 10%), the target database cannot keep up with the incoming data, leading to increased latency and reduced throughput. This is a common performance issue in DMS migrations where the target's provisioned IOPS are exhausted, especially during large data loads.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The source database has large LOBs that are being transferred in full LOB mode.
Why it's wrong here
Large LOBs can slow migration but would cause higher CPU usage.
- ✗
The target database engine is not compatible with DMS.
Why it's wrong here
DMS supports Oracle to PostgreSQL migration.
- ✗
The DMS task is not configured to use parallel tables.
Why it's wrong here
Parallel load could help, but the symptom suggests target throttling.
- ✓
The target RDS instance is throttling write operations due to low IOPS.
Why this is correct
Low IOPS on the target can cause DMS to wait, leading to low CPU on the replication instance.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DBS-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DBS-C01 exam.