- A
The source Oracle database does not have archivelog enabled.
Why wrong: Archivelog is needed for CDC, but the error specifically mentions 'missing table', not log availability.
- B
The Cloud SQL instance does not have enough storage to accommodate CDC logs.
Why wrong: Insufficient storage would cause a different error, typically storage full.
- C
The DMS connection profile for the source is misconfigured.
Why wrong: Connection profile issues would likely cause earlier failures during full dump or connectivity checks.
- D
Some tables in the source database lack primary keys or a valid replica identity.
CDC requires a primary key or replica identity to track changes; without it, DMS cannot replicate changes.
Question 938 of 999
PCD Migrate Data Solutions Practice Question
This PCD practice question tests your understanding of migrate data 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.
During an Oracle to Cloud SQL for PostgreSQL migration using DMS, the full dump phase completes successfully, but the CDC phase fails with a 'missing table' 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
✓
Some tables in the source database lack primary keys or a valid replica identity.
CDC typically requires a primary key or replica identity on each table to track changes. If tables lack these, CDC may fail. DMS expects tables to have primary keys or a valid replica identity for logging.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 Oracle database does not have archivelog enabled.
Why it's wrong here
Archivelog is needed for CDC, but the error specifically mentions 'missing table', not log availability.
- ✗
The Cloud SQL instance does not have enough storage to accommodate CDC logs.
Why it's wrong here
Insufficient storage would cause a different error, typically storage full.
- ✗
The DMS connection profile for the source is misconfigured.
Why it's wrong here
Connection profile issues would likely cause earlier failures during full dump or connectivity checks.
- ✓
Some tables in the source database lack primary keys or a valid replica identity.
Why this is correct
CDC requires a primary key or replica identity to track changes; without it, DMS cannot replicate changes.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
- Standard ACLs match source addresses.
- Extended ACLs can match source, destination, protocol and ports.
- The first matching ACL entry is used.
- There is usually an implicit deny at the end.
TExam Day Tips
- Check inbound versus outbound direction.
- Read the ACL from top to bottom.
- Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCD ACL questions on filtering logic and placement.
- →
Migrate Data Solutions — study guide chapter
Learn the concepts, then practise the questions
- →
Migrate Data Solutions practice questions
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FAQ
Questions learners often ask
What does this PCD question test?
Migrate Data Solutions — This question tests Migrate Data Solutions — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Some tables in the source database lack primary keys or a valid replica identity. — CDC typically requires a primary key or replica identity on each table to track changes. If tables lack these, CDC may fail. DMS expects tables to have primary keys or a valid replica identity for logging.
What should I do if I get this PCD question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCD ACL questions on filtering logic and placement.
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?
Standard ACLs match source addresses.
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Last reviewed: Jul 4, 2026
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