Question 186 of 1,711
DEA-C01 Data Operations and Support Practice Question
A data engineer is troubleshooting an Amazon Redshift cluster that is running slowly. The cluster has 4 dc2.large nodes. The engineer runs a query that scans a large table and notices that the query uses only a single slice instead of all slices. The table is distributed with DISTSTYLE ALL. What is the most likely reason for the query using only one slice?
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
✓
The table uses DISTSTYLE ALL, which stores the entire table on a single slice per node.
DISTSTYLE ALL replicates the entire table to every node, but within each node, the data is stored on a single slice. For dc2.large nodes, which have 2 slices per node, this means that a full table scan will only use one slice per node, not all available slices. This leads to underutilization and slow query performance. Option A is incorrect because the leader node does not execute data queries; it only coordinates them. Queries are executed on compute nodes. Option C is incorrect because WLM queue slots control concurrency, not the number of slices used by a single query. Option D is incorrect because sort keys affect data ordering and compression, not slice distribution.
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 query is running on the leader node instead of the compute nodes.
Why it's wrong here
The leader node distributes queries to compute nodes; the query is running on compute nodes but only one slice per node.
- ✓
The table uses DISTSTYLE ALL, which stores the entire table on a single slice per node.
Why this is correct
DISTSTYLE ALL replicates the table to each node, but it is stored on one slice per node, limiting parallelism.
- ✗
The workload management (WLM) queue is configured with a single query slot.
Why it's wrong here
WLM queue slots affect concurrent query execution, not slice utilization for a single query.
- ✗
The table does not have a sort key defined.
Why it's wrong here
Missing sort key affects performance but does not cause single-slice usage.
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Last reviewed: Jun 20, 2026
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