2.4. Disconnecting
There is a difference between “disconnecting from the database” and exiting the SQL*Plus application. When you use the EXIT command:
Any database changes you submitted, such as INSERT statements, are committed; that is, they are permanently applied to the database. This is because SQL*Plus does an implicit commit when you end your session.
Your point-to-point session is terminated.
Finally, your SQL*Plus program exits and you are back to your desktop or command shell.
From within SQL*Plus, you do have the option to just DISCONNECT from your current database connection but keep the SQL*Plus application up. When you disconnect:
Any database changes you submitted, such as INSERT statements, are committed; that is, they are permanently applied to the database.
Your point-to-point session is terminated.
You are still within the SQL*Plus application but you no longer have a connection to a database. From this point you can reconnect to the same database, connect to a different database, or exit from SQL*Plus with the exit command.
Whether you DISCONNECT or you EXIT, SQL*Plus does an implicit commit.