There are the following steps of shutting down the database.
1)Close the database.
2) Unmount the database.
3)Shut down the instance.
1) Close a database:
When we close the database, oracle writes all the data and recovery data in the SGA to the datafiles and redo log files. Next orcale close all online datafiles and redo log files.
Any offline datafiles of any offline tablespace have been closed already.
2) Unmount the database:
After the database has been closed, Oracle unmount the database to dissociate it from its instance. At this point, instance remains in the memory of the computer.
After the database is unmounted, Oracle closes the control files of the database.
3) Shut down an Instance:
The final step in the shut down the database is the shutting down an instance, The SGA is removed from the memory and the background processes are terminated.