This PL-300 practice question tests your understanding of prepare the data. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 Power BI dataset is configured to use Import storage mode. The dataset includes a fact table with 100 million rows and several dimension tables. The report is slow when users interact with visuals. You need to improve query performance without changing the storage mode. Which action should you take?
Create aggregations on the fact table.
Aggregations pre-summarize data, improving query speed.
Increase the scheduled refresh frequency.
Why wrong: Does not affect query performance.
Reduce the number of dimension tables.
Why wrong: May break relationships and not directly improve performance.
Enable 'Load to report' for all tables.
Why wrong: Unrelated to query performance.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Create aggregations on the fact table.
Creating aggregations on the fact table allows Power BI to pre-summarize data at higher granularity levels, reducing the amount of data scanned during query execution. Since the dataset uses Import mode, aggregations leverage the in-memory columnar storage to serve queries from pre-computed tables, significantly improving visual response times without altering the storage mode.
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.
Create aggregations on the fact table.
Why this is correct
Aggregations pre-summarize data, improving query speed.
Related concept
Read the scenario before looking for a memorised answer.
Increase the scheduled refresh frequency.
Why it's wrong here
Does not affect query performance.
Reduce the number of dimension tables.
Why it's wrong here
May break relationships and not directly improve performance.
Enable 'Load to report' for all tables.
Why it's wrong here
Unrelated to query performance.
Common exam traps
The trap here is that candidates often confuse data refresh frequency (Option B) with query performance, or mistakenly think reducing dimensions (Option C) is a valid optimization, when in fact aggregations are the correct technique for speeding up Import mode queries.
Detailed technical explanation
Aggregations in Power BI work by creating materialized pre-aggregated tables that the VertiPaq engine queries first, falling back to the full fact table only when necessary. For a 100-million-row fact table, a well-designed aggregation at a higher grain (e.g., daily instead of transactional) can reduce query time from seconds to milliseconds. The engine uses a 'matching' process based on the granularity of the query, and aggregations can be stored in Import mode or DirectQuery mode, but here Import mode is preserved.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
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FAQ
Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..
The correct answer is: Create aggregations on the fact table. — Creating aggregations on the fact table allows Power BI to pre-summarize data at higher granularity levels, reducing the amount of data scanned during query execution. Since the dataset uses Import mode, aggregations leverage the in-memory columnar storage to serve queries from pre-computed tables, significantly improving visual response times without altering the storage mode.
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 11, 2026
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