- A
The VPC peering connection between on-premises and AWS is down.
Why wrong: Would cause connectivity error, not missing changes.
- B
The DMS task's table mapping is incorrectly configured.
Why wrong: Would cause specific tables to be missing, not changes.
- C
DMS is not publishing task logs to CloudWatch Logs.
Why wrong: CloudWatch logging is for monitoring, not capturing changes.
- D
The source Oracle database is not configured to retain archived redo logs for a sufficient period.
DMS requires archived logs to capture changes; if logs are purged, changes are lost.
Question 939 of 1,786
DEA-C01 Data Ingestion and Transformation Practice Question
This DEA-C01 practice question tests your understanding of data ingestion and transformation. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company uses AWS DMS to migrate data from an on-premises Oracle database to Amazon RDS for PostgreSQL. The migration is ongoing with continuous replication. The data engineer notices that some changes are not being captured in the target database. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 source Oracle database is not configured to retain archived redo logs for a sufficient period.
In AWS DMS continuous replication (CDC), the service reads changes from the source Oracle database's archived redo logs. If the logs are rotated or deleted before DMS has a chance to process them, changes are lost. Option D is correct because insufficient retention of archived redo logs is the most likely cause of missing changes in the target.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 VPC peering connection between on-premises and AWS is down.
Why it's wrong here
Would cause connectivity error, not missing changes.
- ✗
The DMS task's table mapping is incorrectly configured.
Why it's wrong here
Would cause specific tables to be missing, not changes.
- ✗
DMS is not publishing task logs to CloudWatch Logs.
Why it's wrong here
CloudWatch logging is for monitoring, not capturing changes.
- ✓
The source Oracle database is not configured to retain archived redo logs for a sufficient period.
Why this is correct
DMS requires archived logs to capture changes; if logs are purged, changes are lost.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume missing changes are due to network or configuration errors (like VPC or table mapping), but the real issue is the source database's log retention policy, which is a subtle but critical requirement for CDC with DMS.
Detailed technical explanation
How to think about this question
DMS uses Oracle LogMiner or binary reader to extract changes from archived redo logs. The default retention for Oracle archived logs is often only 24 hours or based on disk space; if DMS falls behind due to high transaction volume or network latency, logs may be purged before being read. In production, setting `db_recovery_file_dest_size` and `log_archive_dest` retention to at least 48–72 hours is a common best practice to avoid data loss during CDC.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Data Ingestion and Transformation — study guide chapter
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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Ingestion and Transformation — This question tests Data Ingestion and Transformation — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The source Oracle database is not configured to retain archived redo logs for a sufficient period. — In AWS DMS continuous replication (CDC), the service reads changes from the source Oracle database's archived redo logs. If the logs are rotated or deleted before DMS has a chance to process them, changes are lost. Option D is correct because insufficient retention of archived redo logs is the most likely cause of missing changes in the target.
What should I do if I get this DEA-C01 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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