How to open oracle database

I have always felt a little confused about the various startup and shutdown commands of the database. Let me sort them out now.

1. Database startup:

Oracle startup is divided into three steps: starting the instance, loading the database, and opening the database. You can open the database according to your actual needs

The syntax is startup

1, nomount mode

SQL> startup nomount
ORACLE instance started.

Total System Global Area  830930944 bytes
Fixed Size                  2257800 bytes
Variable Size             536874104 bytes
Database Buffers          285212672 bytes
Redo Buffers                6586368 bytes

This startup method only creates instances (that is, various methods for creating Oracle instances) memory structures and service processes), does not load the database or open data files.

This mode is generally suitable for creating databases and control files.

2. Mount mode

SQL> startup mount
ORACLE instance started.

Total System Global Area  830930944 bytes
Fixed Size                  2257800 bytes
Variable Size             536874104 bytes
Database Buffers          285212672 bytes
Redo Buffers                6586368 bytes
Database mounted.

This mode will start the instance, load the database and save the database shutdown mode

Generally used for database maintenance, such as: performing database complete Recovery operations, changing the archive mode of the database, etc.

3. Open mode

SQL> startup
ORACLE instance started.

Total System Global Area  830930944 bytes
Fixed Size                  2257800 bytes
Variable Size             536874104 bytes
Database Buffers          285212672 bytes
Redo Buffers                6586368 bytes
Database mounted.
Database opened.

This mode will start the instance, load and open the database. This is the conventional way to open a database. As long as the user wants to perform multiple operations on the database, it must be opened in this way. (Open the database in open mode) No parameters are required after startup.

4. Force mode

SQL> startup force
ORACLE instance started.

Total System Global Area  830930944 bytes
Fixed Size                  2257800 bytes
Variable Size             536874104 bytes
Database Buffers          285212672 bytes
Redo Buffers                6586368 bytes
Database mounted.
Database opened.

This mode will terminate the instance and restart the database (open). This mode has certain mandatory requirements (for example, you can try it when other startup modes fail. This mode)

Recommended tutorial: "Oracle Tutorial"

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