- A
Change the table design to use DISTKEY and SORTKEY.
Why wrong: Table design changes require table recreation and do not immediately reduce disk usage.
- B
Enable compression on all columns.
Why wrong: Compression is typically set at table creation; existing tables may already be compressed.
- C
Increase the number of nodes to 8.
Adding nodes increases disk capacity and I/O throughput, reducing disk pressure and improving query performance.
- D
Run the VACUUM command to reclaim space.
Why wrong: VACUUM cleans up deleted rows but does not reduce overall data volume.
Question 411 of 1,786
DEA-C01 Data Operations and Support Practice Question
This DEA-C01 practice question tests your understanding of data operations and support. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 data engineer is monitoring a Redshift cluster that is experiencing slow query performance. The cluster has 4 dc2.large nodes. The engineer notices that disk space usage is at 85% across all nodes. Which action would MOST likely improve query performance?
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
✓
Increase the number of nodes to 8.
At 85% disk usage on dc2.large nodes, the cluster is approaching the threshold where Redshift begins to automatically offload data to Amazon S3, causing significant performance degradation due to increased I/O and network latency. Adding more nodes (option C) increases both compute capacity and total disk space, reducing per-node disk pressure and allowing the cluster to keep more data local for faster query execution.
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.
- ✗
Change the table design to use DISTKEY and SORTKEY.
Why it's wrong here
Table design changes require table recreation and do not immediately reduce disk usage.
- ✗
Enable compression on all columns.
Why it's wrong here
Compression is typically set at table creation; existing tables may already be compressed.
- ✓
Increase the number of nodes to 8.
Why this is correct
Adding nodes increases disk capacity and I/O throughput, reducing disk pressure and improving query performance.
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.
- ✗
Run the VACUUM command to reclaim space.
Why it's wrong here
VACUUM cleans up deleted rows but does not reduce overall data volume.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The DEA-C01 exam often tests the misconception that VACUUM or table design optimizations can resolve capacity-related performance issues, when in fact the immediate root cause is disk pressure triggering S3 offloading, which only scale-out or resize can fix.
Detailed technical explanation
How to think about this question
Redshift dc2.large nodes have approximately 160 GB of SSD storage per node. When disk usage exceeds 80%, Redshift begins to offload colder data to S3, which introduces latency for queries that need that data. Adding nodes not only increases total storage (e.g., from 640 GB to 1.28 TB) but also distributes the data across more slices, improving parallelism and reducing the likelihood of S3 offloading. In practice, monitoring disk usage and scaling out before hitting 80% is a key operational best practice.
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.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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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FAQ
Questions learners often ask
What does this DEA-C01 question test?
Data Operations and Support — This question tests Data Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Increase the number of nodes to 8. — At 85% disk usage on dc2.large nodes, the cluster is approaching the threshold where Redshift begins to automatically offload data to Amazon S3, causing significant performance degradation due to increased I/O and network latency. Adding more nodes (option C) increases both compute capacity and total disk space, reducing per-node disk pressure and allowing the cluster to keep more data local for faster query execution.
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.
About these practice questions
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Last reviewed: Jul 4, 2026
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