What do these Copy Only Backup options mean?

Question

I am currently trying to backup an empty SQL Server 2008 R2 database that I designed for a project that is getting shelved for the time being. I was going through the back up pr

Answer 1

Normally when you take a backup, it starts (or continues, depending on the type of backup that you took) what is called a log chain. Let's say that you need a copy of your database and, for whatever reason, you can't use your normally scheduled backups for this purpose. Let's walk through the scenario where you don't use a copy_only backup

1. Normal full backup
2. A bunch of differential backups
3. Another full backup (to make your copy database)
4. More differential backups
5. Delete the backup from step 3 (you know... to save space)
6. Disaster on your actual database that necessitates restore from backup

In this case, you can only restore to the last differential backup made in step 2 because the differential backups made in step 4 depend on the full backup from step 3. Now, if the backup in step 3 were a copy_only backup, you'd be fine because you're not re-establishing a log chain (which is to say that the differential backups in step 4 depend on the full backup from step 1.