Oracle database: Key concepts

What is a tablespace?

A database is divided into one or more logical storage units called tablespaces, which group physical structures together. The size of the tablespace is the combined size of the datafiles that constitute the tablespace.

What is a datafile?

Each tablespace in a database consists of one or more files called datafiles. Datafiles store the database’s data. A datafile can be associated with only one tablespace and only one database. For example, a database can have six tablespaces each consisting of multiple datafiles.

What is a disk?

The medium on which datafiles are stored.

What is a control file?

The control file of a database contains entries that specify the physical structure of the database. For example, it contains the following types of information:

• Database name

• Names and location of datafiles and redo logs

• Timestamp of database creation

During normal recovery procedures, the information in a control file is used to guide the automated progression of the recovery operation.

What is a redo log?

Redo logs, also called transaction log files, are generated by the database as it processes transactions. Redo logs are used to recover the database. The redo logs generated since the most recent backup restore the database to the point before the failure.

The database has a limited number of redo logs (three to five, depending on the size of the database). As the redo log files fill up, they are archived and become archived redo log files.

What is RMAN?

Oracle Recovery Manager, or RMAN, is the Oracle-preferred method for efficiently backing up and recovering the Oracle database. RMAN offers features not available through user-managed methods, such as parallelization of backup/recovery data streams, backup files retention policy, and detailed history of all backups.