From BOL... my favorite resource :D
Truncating the transaction log:
Code:
BACKUP LOG { database_name | @database_name_var }
{
[ WITH
{ NO_LOG | TRUNCATE_ONLY } ]
}
NO_LOG | TRUNCATE_ONLY
Removes the inactive part of the log without making a backup copy of it and truncates the log. This option frees space. Specifying a backup device is unnecessary because the log backup is not saved. NO_LOG and TRUNCATE_ONLY are synonyms.
After backing up the log using either NO_LOG or TRUNCATE_ONLY, the changes recorded in the log are not recoverable. For recovery purposes, immediately execute BACKUP DATABASE.
And, no, I've never heard nor have ever seen that you need to do at least 2 backups to clear the log... it has always worked on the first backup on every database I've ever worked with.
--Jeff Moden