- A
The source database has a firewall blocking the DMS IP address.
Why wrong: Firewall issues typically cause connection timeouts, not relation OID errors.
- B
The source database does not have the pglogical extension installed.
Why wrong: Missing extension would cause a different error about the extension itself.
- C
The target AlloyDB cluster does not have the pglogical extension.
Why wrong: AlloyDB uses built-in logical replication; pglogical is not required on target.
- D
A DDL operation on the source dropped or altered a table after the replication slot was created.
DDL changes invalidate the replication slot, causing the relation OID error.
Question 143 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 company is migrating an on-premises PostgreSQL 13 database to AlloyDB for PostgreSQL using DMS continuous migration. The source is configured with logical replication using the pglogical extension. During the initial sync, the migration job fails with the error 'could not open relation with OID xxxx'. 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
✓
A DDL operation on the source dropped or altered a table after the replication slot was created.
DMS uses logical replication slots when possible. If the source has DDL changes (e.g., table dropped) after the slot is created, the replication slot may become invalid.
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 source database has a firewall blocking the DMS IP address.
Why it's wrong here
Firewall issues typically cause connection timeouts, not relation OID errors.
- ✗
The source database does not have the pglogical extension installed.
Why it's wrong here
Missing extension would cause a different error about the extension itself.
- ✗
The target AlloyDB cluster does not have the pglogical extension.
Why it's wrong here
AlloyDB uses built-in logical replication; pglogical is not required on target.
- ✓
A DDL operation on the source dropped or altered a table after the replication slot was created.
Why this is correct
DDL changes invalidate the replication slot, causing the relation OID error.
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
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 healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
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.
- →
Migrate Database Solutions — study guide chapter
Learn the concepts, then practise the questions
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Migrate Database Solutions practice questions
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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: A DDL operation on the source dropped or altered a table after the replication slot was created. — DMS uses logical replication slots when possible. If the source has DDL changes (e.g., table dropped) after the slot is created, the replication slot may become invalid.
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
This PCDOE practice question is part of Courseiva's free Google Cloud 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 PCDOE exam.
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