When troubleshooting slow DAX queries, sharing the right diagnostic information with an expert can make all the difference. That’s where a DAXX file comes in. This special file format is created using DAX Studio. It bundles essential metadata and performance details without exposing query results. It’s perfect for collaborative optimisation.
What is a DAXX File?
A DAXX file is a diagnostic package generated by DAX Studio. It can include:
- Server Timings – Detailed timings for storage engine and formula engine operations.
- Query Plan – Execution plan showing how the query was processed.
- VPAX Data – VertiPaq Analyzer output, including model structure, row counts, and cardinality stats.
- Query Text – The actual DAX expression you ran.
Importantly, it does not include query results, so sensitive data stays out of the file.
Experts use this file to locate bottlenecks and suggest improvements to your query or model design.
When Should You Create a DAXX File?
If you face a slow DAX query, it might be flagged by Performance Analyzer in Power BI Desktop. You can capture that query and run it in DAX Studio to help prepare a DAXX file for review.
Steps to Generate a DAXX File in DAX Studio
- Open DAX Studio and connect to your model. Paste the slow DAX query you want to analyse.
- On the Home toolbar:
- Clear on Run: Enable this to reset earlier queries.
- Server Timings: Click to start capturing detailed timings.
- Query Plan: Enable to record the execution plan
- Capture VPAX:
- Go to Advanced → Export VPAX.
- This collects model metadata and statistics.
- Run the Query:
- Execute the DAX expression while tracing is active.
- Execute the DAX expression while tracing is active.
- Save as DAXX:
- Use File → Save As → DAXX.
- This format includes all diagnostics (timings, plan, VPAX) but excludes query results
Tip: DAXX format is not the default save choice—make sure you select it explicitly.
Why Share a DAXX File?
A skilled DAX expert (or automated agent) can review the file and offer actionable recommendations, like:
- Optimising filter context.
- Reducing cardinality issues.
- Improving storage engine performance
- Model improvements
Summary
The DAXX file is your go-to diagnostic bundle for performance tuning. By doing these steps, you’ll give experts with everything they need—without exposing sensitive data.