Today we will see the basic terms regarding the oracle database i.e. Oracle Instance, Oracle Database and Oracle Server. Many peoples are always having confusion between Oracle Instance, Oracle Database and Oracle Server. Below is the simple description for all these three terms.
1. Oracle Instance:-
- Oracle instance is combination of memory structures and background processes.
- When Oracle instance is started, System Global Area(SGA) is allocated and background processes are started.
- Instance can open and use only one database at a time.
- We can not access data from database without starting up oracle instance.
2. Oracle Database:-
Oracle database consist operating system files known as database files which provides actual storage information. Oracle database has physical and logical structure. An oracle database consist of three types of files
- Data Files: These files contains actual data in the database.
- Redo Files: These files contains changes made to the data in the database. This information requires for database recovery in case of instance failure.
- Control Files: These files contains information which is necessary to maintain and integrity of database.
3. Oracle Server:-
Oracle server is combination of Oracle Instance and Oracle Database.