DEA-C01 Data Ingestion and Transformation Practice Question
A company uses AWS DMS to migrate an on-premises Oracle database to Amazon RDS for PostgreSQL. The migration completes, but the target table has more rows than the source. Which is the MOST likely cause?
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
✓
Target tables lack unique constraints, causing DMS to insert duplicate rows.
When target tables lack unique constraints (like primary keys or unique indexes), AWS DMS cannot identify duplicate records during change data capture (CDC). If the same change is applied multiple times (e.g., due to recovery after a failure), DMS may insert duplicate rows, causing the target to have more rows than the source. Option A is incorrect because binary replication is not used; DMS uses logical replication. Option B is incorrect because case sensitivity differences could lead to missing rows, not extra rows. Option C is incorrect because a full load alone would not cause duplicates; the issue arises during ongoing replication without unique constraints.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DMS used binary replication which included extra metadata rows.
Why it's wrong here
Binary replication is not a standard DMS feature; it would not add rows.
- ✗
Oracle and PostgreSQL handle case sensitivity differently.
Why it's wrong here
Case sensitivity differences cause data mismatches, not extra rows.
- ✗
DMS performed a full load instead of ongoing replication.
Why it's wrong here
A full load would not create duplicates; it replaces data.
- ✓
Target tables lack unique constraints, causing DMS to insert duplicate rows.
Why this is correct
Without unique constraints, DMS may re-apply changes and create duplicates.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-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 DEA-C01 exam.