Automatic Clustering is transparent and does not block DML statements issued against tables while they are being reclustered.

• A. False
• B. True
• C. Only blocks writes
• D. Only for reads

Answer: (B)

Automatic Clustering runs in the background and is designed to be transparent to your workloads. It continuously reclusters micro-partitions to align data with the defined clustering key, but this work doesn’t block DML operations. Reads and writes can proceed while reclustering occurs, thanks to Snowflake’s MVCC and the separate clustering service coordinating partition rewrites. As a result, DML statements issued against the table continue to execute normally, and queries reflect both the existing data and the improvements from ongoing reclustering over time. In practice, there might be some minor resource overhead, but the DML capability itself remains uninterrupted.