I'm studying for the 70-432 (SQL Server 2008) exam, and I'm a bit confused about how the transaction log works.
From what I understand, (correct me if I'm wrong...) the log is actively stored in memory and copied to a file on the drive as often as possible. At every checkpoint, complete transactions are committed to the data file on the hard drive (that is, they're not actually written to the drive at all until the checkpoint. And the tail always holds the transactions that have not been committed yet.
When a disaster happens, and you try to backup the "tail" of the log. Is that stored in a file, or are you trying to dump from memory? I'm aware that this is not always possible to do, but it's highly advisable to try to do it.
Am I right in this understanding?