High Virtual Log File (VLF) Count

VLF stands for Virtual Log File and the transaction log file is made up of one or more virtual log files. The number of virtual log files can grow based on the autogrowth settings for the log file and how often the active transactions are written to disk.  Too many virtual log files can cause transaction log backups to slow down and can also slow down database recovery, and in extreme cases, even affect insert/update/delete performance.

To find it, check the number of virtual log files (VLFs) in each database and alerts when there’s 1,000 or more. Right at 1,000 may not be a problem based on your database size – we just want to bring the problem up before it becomes critical, since fixing this issue is a pain in the rear.

To Fix the Problem

Bad news: we’re going to have some downtime.  The whole server doesn’t have to be down, but to fix this, we have to shrink and regrow the log file – and that’s a blocking operation.  To learn how, check out Dave Levy’s post on A Busy/Accidental DBA’s Guide to Managing VLFs.

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