The Subtleties of COPY_ONLY Backups
Recently I have been looking at the COPY_ONLY feature for taking backups of a database. COPY_ONLY was introduced in SQL Server 2005, and allows you to take ad-hoc backups of either the log or a full backup without breaking the backup chain for differential backups. The COPY_ONLY backup is not part of the restore log: so when restoring from a full backup you can ignore it. The same here can also be said for log COPY_ONLY backups; it's an ad-hoc backup that does not alter the transaction log at all; there's no clearing down of the log.