The answer is to run the VACUUM command on the tables. This is the most effective action because a high unsorted percentage in svv_table_info indicates that data rows are stored out of order across disk blocks, forcing Redshift to scan more blocks than necessary during queries. The VACUUM operation physically re-sorts the data according to the table’s sort key and reclaims deleted space, directly addressing the root cause of slow scans. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Redshift maintenance operations and the difference between VACUUM and ANALYZE—a common trap is confusing ANALYZE (which only updates statistics) with VACUUM (which physically reorganizes data). Remember that unsorted data is a storage-level problem, not a statistics problem. Memory tip: VACUUM sorts the “vacuum” of space, while ANALYZE only analyzes the map.
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 company runs a data warehouse on Amazon Redshift. The data engineer notices that some queries are running slowly. Upon reviewing the system tables, the engineer finds that the 'svv_table_info' shows high 'unsorted' percentage for several large tables. What is the MOST effective action to improve query performance?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run the VACUUM command on the tables.
Option B is correct because VACUUM sorts the data and reclaims space, improving query performance. Option A is wrong because ANALYZE updates statistics but does not sort. Option C is wrong because increasing the number of nodes may help but is not the most direct fix for unsorted data. Option D is wrong because changing distribution style would require recreating the table.
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.
✗
Run the ANALYZE command on the tables.
Why it's wrong here
ANALYZE updates statistics but does not sort data.
✓
Run the VACUUM command on the tables.
Why this is correct
VACUUM sorts the data, improving query performance.
Related concept
Read the scenario before looking for a memorised answer.
✗
Change the distribution style of the tables to ALL.
Why it's wrong here
Changing distribution style requires table redesign.
✗
Increase the number of nodes in the Redshift cluster.
Why it's wrong here
More nodes help with overall performance but not specifically unsorted data.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which DEA-C01 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.
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: Run the VACUUM command on the tables. — Option B is correct because VACUUM sorts the data and reclaims space, improving query performance. Option A is wrong because ANALYZE updates statistics but does not sort. Option C is wrong because increasing the number of nodes may help but is not the most direct fix for unsorted data. Option D is wrong because changing distribution style would require recreating the table.
What should I do if I get this DEA-C01 question wrong?
Identify which DEA-C01 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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company uses Amazon Redshift for its data warehouse. A data engineer notices that queries are running slowly and the system's disk space is nearly full. The engineer runs the STV_PARTITIONS view and sees that many slices have high 'tossed' counts. What does this indicate, and what should the engineer do?
medium
A.The tossed rows are permanent and cannot be reclaimed; the engineer should perform a deep copy to a new table.
B.The tossed rows indicate that the sort key is not optimal; redefining the sort key will reduce tossed rows.
C.The tossed rows are due to data skew; redistribute the table on a different distribution key.
✓ D.The tossed rows are deleted rows that need to be reclaimed by running VACUUM.
Why D: Option A is correct because 'tossed' rows indicate data that was deleted or updated and is waiting for VACUUM. A high tossed count means wasted space. Running VACUUM reclaims that space. Option B is wrong because 'tossed' does not indicate sort key issues. Option C is wrong because 'tossed' is not about distribution. Option D is wrong because deep copy is a more drastic alternative, but VACUUM is the standard action.
Last reviewed: Jun 20, 2026
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This DEA-C01 practice question is part of Courseiva's free Amazon Web Services 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 DEA-C01 exam.
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