Backup strategy with RMAN

[marist89]

Level 0 = Full backup = Hot backup. The three terms can be used interchangeably.

I don't have a problem with you backing up to disk, I do it myself. The major advantages to using an incremental backup are that you save space at your destination and transmit less data to your "slower" devices to write. Typically, you would want to implement incremental backups when you backup over a network to tape. Here, the bandwidth of the network is (probably) your bottleneck followed by speed at which your tape drives can stream data. Using an incremental backup will send less data to your tape devices to write.

Using incremental backups with disk-to-disk backups (IMHO) is pointless. First, you are most likely backing up to the local machine so network speed is irrelevent. Second, your destination disks are many times faster than any tape device and therefore can handle the load. Lastly, if you are doing a full backup at some point during the week, you obviously have the space, so there's no need to save space.

In either case, RMAN has to read through the entire database (more or less) to find out which blocks to write. Since this is the majority of the work (in a disk-to-disk backup), the time to backup will be similar in either scenario.

Incremental restores are slow. First you have to apply the last full backup. Then you might have to apply something from an incremental backup. Then you might have to apply something from a different incremental backup. If your Mean Time To Restore (MTTR) is short, full backups are the only way to go.

In addition, incremental restores are error prone for beginner DBAs. When you have declared a recovery, the last thing you want to do is worry about when your last successful full backup was. Save yourself the trouble and do a full backup every day.

Lastly, don't forget to test and document your backup AND recovery scenarios. I have seen plenty of people put in backup plans only to find they can't recover when the sh#t hits the fan.