Why having too many or too few virtual log files VLFs can lead to performance problems?

Does SQL log file affect performance?

If the transaction log file is full in the SQL Server database, it degrades the performance of the SQL Server. It also slows down the speed of the transactional log backup process. In addition, the over-sized transaction logs decrease the disk space also because old transaction logs are not removed yet.

How reduce high VLF count in SQL Server?

Fixing a database with a high VLF count is a simple process:1Check the current size of the transaction log.2Backup the transaction log.3Shrink the transaction log to as close to 0 KB as possible.4Check that the VLF count is less than 50 (best if less than 10 at this point).Fixing High VLF Counts - Navisite

What happens when log file is full?

When the transaction log becomes full, SQL Server Database Engine issues a 9002 error. The log can fill when the database is online, or in recovery. If the log fills while the database is online, the database remains online but can only be read, not updated.

What is a virtual log file?

A Virtual Log File is a smaller file inside Log file which contains the actual log records which are actively written inside them. New Virtual Log Files are created when the existing ones are already active and new space is required. This brings us to the point where the value of the Virtual Log Files is created.