Quick Answer
The correct action is to run VACUUM DELETE to reclaim disk space without interrupting ongoing queries. This command targets only the space occupied by deleted rows, which Amazon Redshift marks as unavailable but does not physically remove until a vacuum operation occurs. Unlike a full VACUUM, which requires an exclusive table lock and can block reads and writes, VACUUM DELETE operates as a background process that maintains query concurrency, making it ideal for production environments where uptime is critical. On the AWS Certified Data Engineer Associate DEA-C01 exam, this scenario tests your understanding of Redshift’s storage architecture and the distinction between VACUUM DELETE and VACUUM FULL or VACUUM SORT ONLY. A common trap is choosing VACUUM FULL, which reclaims space but locks the table, or assuming ANALYZE alone frees disk space. Remember the mnemonic: “Delete only, don’t delay—VACUUM DELETE works while queries play.”
This DEA-C01 practice question tests your understanding of data store management. 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 uses Amazon Redshift for analytics. A data engineer notices that queries are slow due to high disk usage on the compute nodes. The engineer needs to reclaim disk space without interrupting ongoing queries. Which action should the engineer take?
Use the COPY command to reload data
Why wrong: COPY is for loading data, not reclaiming space.
Run VACUUM FULL on all tables
Why wrong: VACUUM FULL locks tables and may interrupt queries.
Run VACUUM DELETE to reclaim space from deleted rows
VACUUM DELETE reclaims space without exclusive locks and can run concurrently.
Resize the cluster to a larger instance type
Why wrong: Resizing is disruptive and does not reclain space; it adds capacity.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Run VACUUM DELETE to reclaim space from deleted rows
Option C is correct because VACUUM DELETE specifically reclaims disk space from deleted rows without requiring an exclusive table lock, allowing ongoing queries to continue. In Amazon Redshift, deleted rows consume disk space until reclaimed, and VACUUM DELETE operates in the background to free that space while maintaining query concurrency.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use the COPY command to reload data
Why it's wrong here
COPY is for loading data, not reclaiming space.
Run VACUUM FULL on all tables
Why it's wrong here
VACUUM FULL locks tables and may interrupt queries.
Run VACUUM DELETE to reclaim space from deleted rows
Why this is correct
VACUUM DELETE reclaims space without exclusive locks and can run concurrently.
Related concept
Read the scenario before looking for a memorised answer.
Resize the cluster to a larger instance type
Why it's wrong here
Resizing is disruptive and does not reclain space; it adds capacity.
Common exam traps
The trap here is that candidates confuse VACUUM FULL with VACUUM DELETE, assuming any VACUUM operation reclaims space without considering the lock requirement and interruption to queries.
Detailed technical explanation
Amazon Redshift stores data in 1 MB blocks on compute nodes, and deleted rows mark blocks as 'ghost' rows that still occupy space. VACUUM DELETE sorts and merges these blocks to reclaim space without re-sorting the entire table, making it faster and less disruptive than VACUUM FULL. In practice, running VACUUM DELETE periodically after heavy DELETE operations prevents disk bloat while keeping the cluster available for analytics workloads.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
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FAQ
Data Store Management — This question tests Data Store Management — Read the scenario before looking for a memorised answer..
The correct answer is: Run VACUUM DELETE to reclaim space from deleted rows — Option C is correct because VACUUM DELETE specifically reclaims disk space from deleted rows without requiring an exclusive table lock, allowing ongoing queries to continue. In Amazon Redshift, deleted rows consume disk space until reclaimed, and VACUUM DELETE operates in the background to free that space while maintaining query concurrency.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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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