What is the best method of taking backups? We have a database that is 1.4 terabytes with more than 1000 data files. We use the GTAR utility but we don't always get successful backups. Is there a better way of taking backups of such a huge database?
For a database this large, I'd use RMAN to back up the database and perform recovery. If you want an overview of RMAN, I have a paper on my web site (http://www.peasland.net) that gives some notes on setting up and using RMAN. I would also recommend reading the Oracle documentation.
The first thing I'd recommend is to take any tablespaces that have static data and setting them to READ ONLY. In a database that is bigger than one terabyte database, it is highly unlikely that most of that data changes. You can backup a single tablespace quite easily with RMAN. When you back up the full database, you can instruct RMAN to skip those tablespaces marked as READ ONLY, because you've already backed them up!
Another big time saver for the more dynamic tablespaces is to use RMAN's ability to perform incremental backups. This way, RMAN only backups those blocks that have changed since the last backup. With skipping READ ONLY tablespaces and incremental backups, you'd be surprised how quickly you can back up your 1.4 terabyte database.