Sql-server – Microsoft SQL Server || Log Truncation

backupsql servert-sqltransaction-log

I have a database and it is in full recovery model. Transaction log file is restricted to 100 MB.

I inserted some rows to a table in the database. When I see the logspace used using dbcc sqlperf(logspace) it showed the log space used is 60 percent.

Next I did a full backup of the database and restored with new database name. When I see the logspace used using dbcc sqlperf(logspace) it showed the log space used is 9 percent.

Full backups do not truncate the log file. I do not understand why the space used by log files in these two DBs are not the same?

Best Answer

A full backup only backs up enough of the log to restore to the point in time of the backup. Only those committed transactions needed are included in the full backup.