Delta Table Maintenance in Microsoft Fabric - A 2026 Practitioner's Guide
I've been pulling together the current state of Delta table maintenance guidance in Fabric and wrote up everything I wish had been in one place when I started. The short version: the official docs have improved a lot recently, but they're spread across 6-7 different Microsoft Learn pages, a couple of blog posts from Microsoft engineers, and some release note archives. Most practitioners haven't read all of it.
The article covers:
- V-Order and Optimize Write defaults – including why the V-Order default page and the comparison table contradict each other (and which one to trust)
- Auto-Compaction, Adaptive Target File Size, Fast Optimize, and File Level Compaction Target - what they do, what's off by default, and why they belong in your utility notebook.
- Do you still need a scheduled OPTIMIZE job? - yes, but probably not the way you're running it now.
- Liquid Clustering vs partitioning - why Fabric's own docs make no mention of partitioning as a recommended strategy.
- Deletion vectors and their Direct Lake impact - the cold-start overhead that accumulates quietly if you're not running OPTIMIZE before your Power BI refresh.
- A reference section mapping each topic to the specific doc page it came from.
I also flag the March 2026 preview features (Lakehouse Maintenance Activity in Pipelines, SQL Endpoint Refresh Activity) that are relevant here but untested.
Full article here (https://bradcoles-dev.github.io/blog/fabric-delta-table-maintenance.html).
Happy to answer questions or hear pushback from anyone running these settings in production.