You back up a transaction log either through the Enterprise Manager (or Management Studio for SQL Server 2005) or using the BACKUP LOG statement. The second question has no meaning for SQL Server - every database has at least one transaction log file, even in Simple recovery mode. The transaction log contains the information necessary to roll back to a particular point or, in the case of recovering from a failure, to roll forward to a particular point. SQL Server writes what it is going to do to the transaction log directly to the disk, then makes the modifications to the actual data pages in RAM. It can then write the changes to the data pages lazily, knowing that it can always recover the changes if there was a failure. To support roll back, SQL Server records what was there before and what the new data is. If a transaction rolls back (either explicitly through a ROLLBACK TRANSACTION statement, or implicitly when a statement fails), SQL Server simply reads the 'before' image and applies it to the data pages. If you're in Full recovery mode, the transaction log contains 'before' and 'after' images of every row that has been modified since you last backed up the log file. An INSERT has no 'before' image and a DELETE no 'after' image. TRUNCATE operations merely log that the truncation occurred, and I'm not sure that it's possible to undo them. If the database file becomes unusable, but the database is still attached to the server, I believe it is still possible to back up the transaction log; then, you can restore your last full database backup and restore all the transaction log backups in sequence to recover to the point of failure. Bulk recovery mode is the same as full mode, but for BULK INSERT operations, SELECT INTO, CREATE INDEX and operations on text- and image-type columns, the server only records in the transaction logs which pages were affected by the change. When you make a transaction log backup, these pages are copied into the backup file. This does not allow rollback to a point in time, because only the latest versions of the bulk pages were stored. The data file must be available in order to back up the transaction log. In Simple recovery mode, the log contains all the information that the Full model does, but it is automatically truncated on a checkpoint. Space occupied by transactions that had already committed becomes eligible for reuse. Long-running transactions can still cause the transaction log to grow in size. Making a full backup of the data