- A
Use the MANIFEST option to specify the files explicitly
Why wrong: Manifest helps specify files but does not reduce the overhead of many small files.
- B
Use the JSON format instead of CSV to reduce parsing overhead
Why wrong: JSON parsing is generally more overhead than CSV.
- C
Consolidate the small files into fewer, larger files (e.g., 100 files of 10 MB each)
Larger files reduce the overhead of file opening and improve parallelism.
- D
Change the table's distribution style to ALL to avoid data redistribution
Why wrong: Distribution style does not affect COPY performance.
Question 508 of 1,730
DBS-C01 COPY command performance Practice Question
This DBS-C01 practice question tests your understanding of monitoring and troubleshooting. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: cOPY command performance. 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 runs an Amazon Redshift cluster with 8 dc2.large nodes for its data warehouse. The data engineering team loads data daily using COPY commands from S3. Recently, the load times have increased significantly. The cluster's CloudWatch metric 'CPUUtilization' is high during the load. The administrator runs the STL_LOAD_ERRORS table and finds no errors. The SVL_S3LOG shows that the COPY command is scanning many small files. The data in S3 is stored as 10,000 small CSV files (each ~100 KB). Which action will MOST improve the COPY performance?
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
✓
Consolidate the small files into fewer, larger files (e.g., 100 files of 10 MB each)
The correct answer is C. Consolidating many small files into fewer, larger files reduces the overhead of opening and processing numerous small files during the COPY command. Redshift performs better with larger files (e.g., 64 MB to 1 GB) because it can parallelize the load across slices more efficiently. Option A is incorrect because the MANIFEST option helps with specifying files but does not address the root cause of many small files. Option B is incorrect because JSON format typically increases parsing overhead compared to CSV. Option D is incorrect because changing the distribution style to ALL does not improve COPY performance; it affects query performance after data is loaded.
Key principle: COPY command performance
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use the MANIFEST option to specify the files explicitly
Why it's wrong here
Manifest helps specify files but does not reduce the overhead of many small files.
- ✗
Use the JSON format instead of CSV to reduce parsing overhead
Why it's wrong here
JSON parsing is generally more overhead than CSV.
- ✓
Consolidate the small files into fewer, larger files (e.g., 100 files of 10 MB each)
Why this is correct
Larger files reduce the overhead of file opening and improve parallelism.
Related concept
COPY command performance
- ✗
Change the table's distribution style to ALL to avoid data redistribution
Why it's wrong here
Distribution style does not affect COPY performance.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates may confuse the benefit of file format (JSON vs. CSV) with the performance impact of file size. The real issue is the large number of small files, not the format.
Detailed technical explanation
How to think about this question
Treat this as a scenario question. Identify the problem, the constraint, and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- COPY command performance
- File size optimization
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
COPY command performance
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.
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FAQ
Questions learners often ask
What does this DBS-C01 question test?
Monitoring and Troubleshooting — This question tests Monitoring and Troubleshooting — COPY command performance.
What is the correct answer to this question?
The correct answer is: Consolidate the small files into fewer, larger files (e.g., 100 files of 10 MB each) — The correct answer is C. Consolidating many small files into fewer, larger files reduces the overhead of opening and processing numerous small files during the COPY command. Redshift performs better with larger files (e.g., 64 MB to 1 GB) because it can parallelize the load across slices more efficiently. Option A is incorrect because the MANIFEST option helps with specifying files but does not address the root cause of many small files. Option B is incorrect because JSON format typically increases parsing overhead compared to CSV. Option D is incorrect because changing the distribution style to ALL does not improve COPY performance; it affects query performance after data is loaded.
What should I do if I get this DBS-C01 question wrong?
Review cOPY command performance, then practise related DBS-C01 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
COPY command performance
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Last reviewed: Jun 20, 2026
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