Section 15.2. Confusion: The Mysteries of Database Architecture

15.2. Confusion: The Mysteries of Database Architecture

Any system administrator who has been in the business for any length of time can probably tell you how to back up the home directories on any system. Start asking about backing up databases, though, and even the most seasoned veterans may start to squirm. The architecture of a database is a mystery to many administrators. Unfortunately, you really need to understand how the database works to properly recover from a disaster. They know how to back up a filesystem, but ask them to find the backups for data space A in database B in instance C, and they look at you with fear in their eyes! They just don't have any experience in database design, nor do they have time to get that experience. If they work in a heterogeneous shop with more than one database, it gets even harder. Their only hope is that the database administrators know what they are doing.

DBAs know all about database architecture. They also know how to back up their database to disk or maybe to a standalone backup drive. They might not have any experience with commercial backup software or large, automated libraries. If the database is too big to back up to disk, and they don't have a standalone backup drive to back up to, they will have to work with the system administrators (SAs) to get the backup done. The only problem is they don't share a common language with the SAs because the SAs don't understand database architecture.

Database products also differ from one another. Try to get an Informix DBA and an Oracle DBA to agree on what a tablespace is! One of the reasons this is difficult is that different products use the same term for different logical elements. What Informix calls a tablespace, Oracle calls a segment. Don't confuse that, however, with a Sybase segment, which is closer to what Oracle calls a tablespace. Are you confused yet? Don't worry.