Detailed Description about Log File in Sql Server

Hi,

In this post i try to discuss about the log file architecture in sql server.

In Log File each and every transaction will be recorded with an unique number called LSN(Log Sequence Number) Number.

Log file will be splitted into multiple parts called VLF(Virtual Log File)

1.Active VLF
2.Recoverable VLF
3.Reusable VLF
4.Un used VLF

Active VLF : In a VLF transactions are waiting to be deliver some other server due to log shipping or replication is called active VLF.

Recoverable VLF : Once transactions are deliverd to other server then that VLF become a Recoverable VLF.

Reusable VLF : Once we take the log backup then that VLF become a Reusable VLF.

Un Used VLF : Till now we never used that VLF that vlf is called Un Used VLF.