What are VLFs in the transaction log?

VLF stands for Virtual Log File. SQL Server divides each physical transaction log file internally into VLFs.

The number and size of VLFs are influenced by log creation and growth history. Excessive numbers of small VLFs can negatively affect some recovery and log-management operations.

Modern SQL Server versions have improved VLF creation algorithms, but administrators should still size log files sensibly and avoid repeated tiny autogrowth events.