SQL*Plus keeps a copy of the most recently entered SQL statement or PL/SQL block in an internal memory area known as the SQL buffer, often referred to simply as the buffer. The reason for this is simple. SQL*Plus needs a place to store your statement or block until you are finished entering it. SQL*Plus also provides you with the ability to edit the statement in the buffer. This can be a real convenience if you make a mistake halfway through typing a long, multiline query.
Tip
SQL*Plus buffers SQL statements and PL/SQL blocks, but not SQL*Plus commands. For example, the DESCRIBE command would not be buffered, but a SELECT statement would be. To help make the distinction, it may help to think in terms of where the command is executed. If you enter something to be executed by the database server, then it is buffered. If it’s a command local to SQL*Plus, then it is not buffered.
SQL*Plus provides two ways to edit the statement currently in the buffer. The first method is to use the set of line-editing commands built into SQL*Plus. The second method is to use the EDIT command to invoke an operating system-specific text editor, such as Notepad in the Windows environment, or vi under Unix.
Tip
If you are editing a statement in the buffer, be sure you don’t forget yourself and execute any other SQL command. Even a simple SQL command like COMMIT will overwrite the buffer. Commands to SQL*Plus, such as the editing commands, do not affect the buffer.
There are some other useful things you can do because of the buffer. If you have several similar SQL statements to execute, using the buffer can save you the effort of completely typing out each one. You may be able to enter the first statement, execute it, make a minor change, execute the new statement, and so on until you are done. SQL*Plus also allows you to save and load the buffer to and from a text file, allowing you to store frequently executed statements for later use.