- A
The wal_level parameter on the source is set to 'replica' instead of 'logical'.
Logical replication requires wal_level='logical' to decode changes; 'replica' is insufficient.
- B
The source database does not have the pglogical extension installed.
Why wrong: pglogical is not required; DMS uses built-in logical replication via publication/slot.
- C
The destination AlloyDB cluster has insufficient storage capacity.
Why wrong: Storage capacity affects writes but does not cause a slot error; the error is source-side.
- D
The DMS connection profile uses the wrong user credentials.
Why wrong: Incorrect credentials would cause initial connection failure, not a replication slot error after dump.
Question 96 of 1,000
PCDOE Migrate Database Solutions Practice Question
This PCDOE practice question tests your understanding of migrate database solutions. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 team is migrating a PostgreSQL database to AlloyDB using DMS with continuous replication. The source database is configured with logical replication. After starting the migration job, the initial dump completes but CDC replication fails with a replication slot error. 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 wal_level parameter on the source is set to 'replica' instead of 'logical'.
The initial dump completes successfully because it uses a snapshot and does not require logical replication. However, for the CDC (change data capture) phase, DMS relies on logical replication slots to capture ongoing changes. This requires the source PostgreSQL database to have its wal_level parameter set to 'logical'. If it is set to 'replica' (the default), the write-ahead log does not contain the necessary information for logical replication, causing DMS to fail when trying to create or use the replication slot. Therefore, option A is correct.
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 wal_level parameter on the source is set to 'replica' instead of 'logical'.
Why this is correct
Logical replication requires wal_level='logical' to decode changes; 'replica' is insufficient.
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.
- ✗
The source database does not have the pglogical extension installed.
Why it's wrong here
pglogical is not required; DMS uses built-in logical replication via publication/slot.
- ✗
The destination AlloyDB cluster has insufficient storage capacity.
Why it's wrong here
Storage capacity affects writes but does not cause a slot error; the error is source-side.
- ✗
The DMS connection profile uses the wrong user credentials.
Why it's wrong here
Incorrect credentials would cause initial connection failure, not a replication slot error after dump.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 PCDOE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Migrate Database Solutions — study guide chapter
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FAQ
Questions learners often ask
What does this PCDOE question test?
Migrate Database Solutions — This question tests Migrate Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The wal_level parameter on the source is set to 'replica' instead of 'logical'. — The initial dump completes successfully because it uses a snapshot and does not require logical replication. However, for the CDC (change data capture) phase, DMS relies on logical replication slots to capture ongoing changes. This requires the source PostgreSQL database to have its wal_level parameter set to 'logical'. If it is set to 'replica' (the default), the write-ahead log does not contain the necessary information for logical replication, causing DMS to fail when trying to create or use the replication slot. Therefore, option A is correct.
What should I do if I get this PCDOE question wrong?
Identify which PCDOE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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.
About these practice questions
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Last reviewed: Jul 4, 2026
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