Hi Friends,

We can have more than one log file for a database. However, in many cases a single log file suffices. Logically, a log file is divided into a number of virtual log files. The virtual log file concept allows SQL Server to manage various operation on the log file, including checkpoints, various phases of revovery like Analysis, Undo & Redo. With the help of Virtual Log Files (VLFs), potions of the Log file is marked as Active, Recoverable, Reusable & Unused. The number of VLFs range between 2 to 16. I haven’t seen a Database with more than 16 VLFs. When a log file grows and when it is shrunk, it is always in units of VLFs. We can observe the virtual log file using SQL Server DBCC LOGINFO statement.

SQL Server DBCC LOGINFO

 

Amit Bansal
SQL MCM, SQL MVP
Director – eDominer Systems, Peopleware India, SQLMaestros

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SQL Server 2014 In-Memory OLTP - Have You Tested It The Right Way?
SQL Server Training, SQL Performance Tuning, Bangalore January 2014