- A
The network connectivity between Synapse and the storage account is intermittent.
Why wrong: Intermittent network issues would likely cause timeouts or different errors, not a 'location does not exist' error.
- B
The CSV file has an incorrect number of columns or contains a header row that mismatches the schema.
Why wrong: Schema mismatch would cause a different error, such as 'column ordinal' or 'data type conversion' error.
- C
The storage account key used in the external data source has expired.
Why wrong: If the key were expired, all loads would fail, not just one file.
- D
The file is being written to or is locked by another process during the PolyBase read.
The error 'used by another process' indicates a file lock, typically because the file is still being written or another reader has an exclusive lock.
Quick Answer
The answer is that the file is being written to or locked by another process during the PolyBase read. This is the most likely cause because the specific error message, "the location does not exist or is used by another process," directly indicates a file lock conflict. In Azure Data Lake Storage Gen2, when a file like 'sales_20250301.csv' is actively being written by a concurrent pipeline or ETL job, the file is locked by that writing process, preventing PolyBase from accessing it until the write completes. On the DP-203 exam, this scenario tests your understanding of PolyBase concurrency limitations and the importance of file availability timing in dedicated SQL pool ingestion pipelines. A common trap is to suspect permission or path issues, but the fact that other files load successfully rules those out. Remember the memory tip: "If the file is still hot, PolyBase cannot read the lot"—the file must be fully closed before PolyBase can open it.
DP-203 Design and implement data storage Practice Question
This DP-203 practice question tests your understanding of design and implement data storage. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 retail company uses Azure Synapse Analytics dedicated SQL pool to store sales data. The data is loaded nightly from Azure Data Lake Storage Gen2 using PolyBase. Recently, the load process started failing with the error 'External table 'sales' is not accessible because the location does not exist or is used by another process.' You verify that the storage account, container, and file path are correct. The file is a CSV file named 'sales_20250301.csv' and it exists. Other files in the same container load successfully. What is the most likely cause of the error?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 file is being written to or is locked by another process during the PolyBase read.
The error 'location does not exist or is used by another process' specifically indicates that the file is locked by another process. In Azure Data Lake Storage Gen2, when a file is being written or modified, it can be locked by the writing process (e.g., a data ingestion pipeline or another ETL job). PolyBase attempts to read the file while it is still being written, causing the error. Option D correctly identifies this concurrency issue.
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.
- ✗
The network connectivity between Synapse and the storage account is intermittent.
Why it's wrong here
Intermittent network issues would likely cause timeouts or different errors, not a 'location does not exist' error.
- ✗
The CSV file has an incorrect number of columns or contains a header row that mismatches the schema.
Why it's wrong here
Schema mismatch would cause a different error, such as 'column ordinal' or 'data type conversion' error.
- ✗
The storage account key used in the external data source has expired.
Why it's wrong here
If the key were expired, all loads would fail, not just one file.
- ✓
The file is being written to or is locked by another process during the PolyBase read.
Why this is correct
The error 'used by another process' indicates a file lock, typically because the file is still being written or another reader has an exclusive lock.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse file-locking errors with authentication or schema issues, but the specific wording 'used by another process' directly points to a concurrency/lock conflict rather than connectivity or data format problems.
Detailed technical explanation
How to think about this question
PolyBase uses the CREATE EXTERNAL TABLE AS SELECT (CETAS) or COPY INTO command to read files from ADLS Gen2. When a file is locked by another process (e.g., a concurrent write operation using Azure Data Factory or a Spark job), the underlying Hadoop Distributed File System (HDFS) lease mechanism prevents PolyBase from opening the file. This is a common issue in nightly batch loads where multiple processes may overlap. To avoid this, ensure that file writes are completed before PolyBase reads, or use a staging area with file rename patterns.
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 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Design and implement data storage — study guide chapter
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FAQ
Questions learners often ask
What does this DP-203 question test?
Design and implement data storage — This question tests Design and implement data storage — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The file is being written to or is locked by another process during the PolyBase read. — The error 'location does not exist or is used by another process' specifically indicates that the file is locked by another process. In Azure Data Lake Storage Gen2, when a file is being written or modified, it can be locked by the writing process (e.g., a data ingestion pipeline or another ETL job). PolyBase attempts to read the file while it is still being written, causing the error. Option D correctly identifies this concurrency issue.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This DP-203 practice question is part of Courseiva's free Microsoft 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 DP-203 exam.
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