DP-203 Design and implement data storage Practice Question
This DP-203 practice question tests your understanding of design and implement data storage. 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 Synapse Analytics dedicated SQL pool with a large fact table partitioned by month. You notice that queries filtering on a specific month still scan all partitions. The table has a clustered columnstore index. What is the most likely cause?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The columnstore index has a large number of open rowgroups that are not compressed.
Option C is correct because when a clustered columnstore index has a large number of open rowgroups (i.e., rowgroups that have not yet been compressed into columnstore segments), queries may fall back to the delta store, which stores data in a B-tree-like structure. This bypasses partition elimination because the delta store does not maintain the same metadata for partition pruning, causing all partitions to be scanned. Compressing open rowgroups into closed, compressed rowgroups restores proper partition elimination behavior.
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 table is hash-distributed on a column other than date, preventing partition elimination.
Why it's wrong here
Partition elimination works regardless of distribution key.
✗
The statistics on the date column are outdated or missing.
Why it's wrong here
Statistics affect cardinality estimation, not partition elimination.
✓
The columnstore index has a large number of open rowgroups that are not compressed.
Why this is correct
Open rowgroups cause the entire columnstore to be scanned, bypassing partition elimination.
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.
✗
The table is replicated, so partition elimination does not apply.
Why it's wrong here
Replicated tables are replicated to all distributions but still support partition elimination.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume partition elimination is always effective with columnstore indexes, overlooking that unclosed delta store rowgroups can disable this optimization, and they may incorrectly attribute the issue to distribution or statistics.
Detailed technical explanation
How to think about this question
In a clustered columnstore index, data is initially written to a delta store (a B-tree structure) and later compressed into columnstore rowgroups (typically ~1 million rows each). Open rowgroups in the delta store lack the min/max metadata that the columnstore uses for partition elimination, so queries against those rows must scan all partitions. The command `ALTER INDEX REORGANIZE` with `COMPRESS_ALL_ROW_GROUPS = ON` can force compression of open rowgroups, restoring partition pruning. This behavior is specific to Azure Synapse Dedicated SQL Pool and SQL Server columnstore indexes.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this DP-203 question in full detail.
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 columnstore index has a large number of open rowgroups that are not compressed. — Option C is correct because when a clustered columnstore index has a large number of open rowgroups (i.e., rowgroups that have not yet been compressed into columnstore segments), queries may fall back to the delta store, which stores data in a B-tree-like structure. This bypasses partition elimination because the delta store does not maintain the same metadata for partition pruning, causing all partitions to be scanned. Compressing open rowgroups into closed, compressed rowgroups restores proper partition elimination behavior.
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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Question Discussion
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