← DEA-C01·Amazon Web Services

Question 1,151 of 1,786

Data Ingestion and Transformation →mediumMultiple ChoiceObjective-mapped

DMS Duplicate Key Errors Due to Auto-Increment Columns

This DEA-C01 practice question tests your understanding of data ingestion and transformation. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 Oracle to Aurora MySQL. During the ongoing replication, the target table shows duplicate primary key errors. 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.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.

A
DMS is using 'Limited LOB mode' and truncating LOB data, causing row mismatches.
Why wrong: LOB truncation does not cause PK duplicates.
B
The source table has a trigger that inserts additional rows.
Why wrong: Triggers on source are not replicated by DMS.
C
The target table has an auto-increment column, and DMS is inserting explicit values that conflict.
DMS inserts values for the PK, but auto-increment may also generate values, causing duplicates.
D
The DMS task is configured with 'Parallel apply' threads that cause race conditions.
Why wrong: Parallel apply should handle ordering; duplicates are more likely due to auto-increment.

Full breakdown with real-world context →

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 table has an auto-increment column, and DMS is inserting explicit values that conflict.

When DMS replicates into a target table with an auto-increment column, it attempts to insert explicit values from the source. If the target's auto-increment counter has already generated a value matching one of those explicit inserts, a duplicate primary key error occurs. This is the most likely cause because DMS does not automatically skip or re-map auto-increment columns unless explicitly configured.

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.

✗
DMS is using 'Limited LOB mode' and truncating LOB data, causing row mismatches.
Why it's wrong here
LOB truncation does not cause PK duplicates.
✗
The source table has a trigger that inserts additional rows.
Why it's wrong here
Triggers on source are not replicated by DMS.
✓
The target table has an auto-increment column, and DMS is inserting explicit values that conflict.
Why this is correct
DMS inserts values for the PK, but auto-increment may also generate values, causing duplicates.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The DMS task is configured with 'Parallel apply' threads that cause race conditions.
Why it's wrong here
Parallel apply should handle ordering; duplicates are more likely due to auto-increment.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The DEA-C01 exam often tests the misconception that duplicate key errors are caused by data type mismatches or LOB truncation, but the real trap is forgetting that auto-increment columns on the target can conflict with explicit primary key values from the source during ongoing replication.

Detailed technical explanation

How to think about this question

DMS uses a task-level setting called 'TargetTablePrepMode' to control how it handles target tables; when set to 'DO_NOTHING', it assumes the target schema matches the source and does not disable auto-increment. In Aurora MySQL, auto-increment columns generate values independently, so explicit inserts from DMS can collide with the next auto-increment value. A common workaround is to set the target table's auto-increment column to a high starting value or use a separate column for the surrogate key.

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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.

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.

Related DEA-C01 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Data Ingestion and Transformation practice questions

Practise DEA-C01 questions linked to Data Ingestion and Transformation.

Data Operations and Support practice questions

Practise DEA-C01 questions linked to Data Operations and Support.

Data Security and Governance practice questions

Practise DEA-C01 questions linked to Data Security and Governance.

Data Store Management practice questions

Practise DEA-C01 questions linked to Data Store Management.

DEA-C01 fundamentals practice questions

Practise DEA-C01 questions linked to DEA-C01 fundamentals.

DEA-C01 scenario practice questions

Practise DEA-C01 questions linked to DEA-C01 scenario.

DEA-C01 troubleshooting practice questions

Practise DEA-C01 questions linked to DEA-C01 troubleshooting.

Practice this exam

Start a free DEA-C01 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions 20 questions 30 questions 50 questions Timed 30

DEA-C01 practice-test guide →Study guide →Browse all practice tests

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 target table has an auto-increment column, and DMS is inserting explicit values that conflict. — When DMS replicates into a target table with an auto-increment column, it attempts to insert explicit values from the source. If the target's auto-increment counter has already generated a value matching one of those explicit inserts, a duplicate primary key error occurs. This is the most likely cause because DMS does not automatically skip or re-map auto-increment columns unless explicitly configured.

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", "primary". 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.

About these practice questions

Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →

How Courseiva writes practice questions · Editorial policy

Keep practising

Question Discussion

Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.

Loading comments…

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.