When running log backups, it is recommended that you use Backup Exec exclusively to perform log truncations if you decide to truncate the logs. After a transaction log has been truncated by something other than a log backup, you must run a full or differential backup before you run another log backup.
Use the Log No Truncate method only when the database is corrupted or database files are missing. This method backs up transactions that you may not be able to access otherwise when the database is in this state. You can then use this transaction log backup along with the last database backup and any previous transaction log backups to restore the database to the point at which it failed; however, any uncommitted transactions are rolled back. The Log No Truncate method does not remove committed transactions after the log is backed up.
To use the Log No Truncate backup to restore a database, you should also have a database backup that was created before the Log No Truncate backup. The transaction log contains only the log files used in the restore process, which alone are not sufficient to restore a complete database. You must have at least one database backup or a full set of filegroup backups and a log backup of the database to restore a database.