What is Copy-only Backup? Why do you use it?

Copy-only Backup is a way of backing up from a traditional SQL backup method. In general, doing a database backup can affect subsequent backup and restore jobs. However, there are times when you need to make a backup for a specific purpose but don't want to affect your database's original backup and restore plans. Copy-only Backup is to serve this purpose.

In general, when you make a backup of the database, the database starts a new log chain, or continues with the existing log chain (depending on how you used the backup). For example, you need a copy of the database, however, you cannot use the backup that is scheduled for your daily schedule. Let's give you an example of what you don't need to copy-only backup.

1. Perform a normal full backup.
2. Make a bunch of transaction log backup.
3. Do a full backup again (in order to get a copy of the database you want).
4. More transaction log backup.
5. Delete the third step of backup (to save space).
6. The database has a disaster and needs to be recovered from backup.

In this case, you can only restore to the last transaction log backup of step 2nd, because the 4th step of transaction log backup is based on the third step of full backup.

Now, if the 3rd step of backup is copy-only backup, then you have no problem, because you did not re-establish a new log chain.

Resources

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Backup Internals

http://download.microsoft.com/download/E/1/1/E115BA90-08E2-4CFD-B408-46CCB17E706A/ hdi-itpro-technet-mp4video-mcm_13_backupinternalslecture.m4v

Copy-only Backups (SQL Server)

Https://msdn.microsoft.com/en-us/library/ms191495.aspx

What's a Copy only Backup?

Http://stackoverflow.com/questions/19035431/what-is-a-copy-only-backup

What is Copy-only Backup? Why do you use it?