Two SQL*Plus commands, STARTUP and SHUTDOWN, allow you to start and stop an Oracle instance. STARTUP, of course, is the command used to start an instance and open a database. In order to use it, you need to understand the various transitional states a database goes through on the way from being closed to open. These are described next, in Section 10.2.1.
The SHUTDOWN command is used to close a database and stop an instance. There are four ways to stop an instance. First, there is the normal shutdown, which closes a database cleanly and has the least disturbing effect on any current users. Three other options allow you to terminate user connections and shut down an instance more quickly.
There are four states an Oracle database may be in on the continuum between being fully shut down and fully operational. Usually, you want the database to be at one extreme or the other, either fully closed or fully open. However, certain administrative tasks, renaming a datafile, for example, require that the database be in one of the intermediate states.
To understand the four states, you need to know the difference between an Oracle instance and an Oracle database. These terms are often used interchangeably, but each has a precise definition.
Oracle uses the term instance to refer to a set of background processes and their shared memory structures. These background processes are the ones that write data to the database, maintain the ...