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The Oracle Server

The Oracle Server consists of an Oracle instance and an Oracle database.

Oracle instance: Is a means to access an Oracle database. Its Always opens one and only one database. An Oracle instance is the combination of the background processes and memory structures. The instance must be started to access the data in the database. Every time an instance is started, a system global area (SGA) is allocated and Oracle background processes are started.The SGA is a memory area used to store database information that is shared by database processes.

Oracle database: An Oracle database is a collection of data that is treated as a unit. The general purpose of a database is to store and retrieve related information. The database has a logical structure and a physical structure. The physical structure of the database is the set of operating system files in the database.

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