- A
Run CONVERT TO DELTA on the underlying Parquet files.
Why wrong: CONVERT TO DELTA is for converting existing Parquet to Delta format; it does not compact files.
- B
Run OPTIMIZE to compact small files.
OPTIMIZE compacts small files into larger ones, improving read performance.
- C
Run DESCRIBE HISTORY to analyze file sizes.
Why wrong: DESCRIBE HISTORY shows table history, not a performance optimization.
- D
Run VACUUM to delete old files.
Why wrong: VACUUM cleans up files older than retention threshold but does not compact small files.
Question 485 of 851
DP-203 Develop data processing Practice Question
This DP-203 practice question tests your understanding of develop data processing. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You have an Azure Databricks notebook that processes data from a Delta table. The notebook runs slowly due to many small files. You need to optimize the Delta table for faster reads. Which Delta Lake operation should you run?
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
✓
Run OPTIMIZE to compact small files.
The OPTIMIZE command in Delta Lake compacts many small files into larger ones by rewriting data files based on the table's partitioning scheme. This reduces the number of files that need to be read during queries, significantly improving read performance. Since the notebook is slow due to many small files, OPTIMIZE directly addresses the root cause.
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 CONVERT TO DELTA on the underlying Parquet files.
Why it's wrong here
CONVERT TO DELTA is for converting existing Parquet to Delta format; it does not compact files.
- ✓
Run OPTIMIZE to compact small files.
Why this is correct
OPTIMIZE compacts small files into larger ones, improving read performance.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Run DESCRIBE HISTORY to analyze file sizes.
Why it's wrong here
DESCRIBE HISTORY shows table history, not a performance optimization.
- ✗
Run VACUUM to delete old files.
Why it's wrong here
VACUUM cleans up files older than retention threshold but does not compact small files.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse VACUUM (which cleans up old files) with OPTIMIZE (which compacts files), or think DESCRIBE HISTORY is a performance-tuning command rather than a diagnostic tool.
Trap categories for this question
Command / output trap
DESCRIBE HISTORY shows table history, not a performance optimization.
Detailed technical explanation
How to think about this question
Under the hood, OPTIMIZE uses a bin-packing algorithm to group small files into target file sizes (default 256 MB) based on the table's partition columns. It creates a new version of the table with the compacted files, and the Delta transaction log records this as an operation, allowing queries to read the optimized layout without affecting concurrent writes. In real-world scenarios, running OPTIMIZE periodically on streaming or high-frequency ingestion tables can reduce file counts from millions to thousands, dramatically improving query latency.
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.
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
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.
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FAQ
Questions learners often ask
What does this DP-203 question test?
Develop data processing — This question tests Develop data processing — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run OPTIMIZE to compact small files. — The OPTIMIZE command in Delta Lake compacts many small files into larger ones by rewriting data files based on the table's partitioning scheme. This reduces the number of files that need to be read during queries, significantly improving read performance. Since the notebook is slow due to many small files, OPTIMIZE directly addresses the root cause.
What should I do if I get this DP-203 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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