Startup stages of database "Nomount" , "Mount" , "Open"

There are three stages of startup of Oracle database which are as follows below: -

Stage 1) No mount stage: -  In this stage, Oracle reads pfile(parameter file) or spfile(server parameter file) to make the instance up and running.

Instance: - SGA(System Global Area)+Background Process

Note:- In this stage, the only instance will up and running not database.

Location of pfile and spfile: - ORACLE_HOME/dbs

Example: -

Stage 2) Mount stage: - In mount stage, Oracle reads the "Control File" to make the database in mount stage.

Example: -

Stage 3) Open stage: -The final stage is the open stage. In this stage user can connects to the database to perform their activity.

Example: -


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