The help command of SQL Plus
To access the help you need a database connection.
because SQL Plus will fired the following SQL in order to retrieve the documentation.
SELECT
INFO
FROM
SYSTEM.HELP
WHERE
UPPER( TOPIC ) LIKE :1
ORDER BY
TOPIC,
SEQ;
help index
help command
To install the help on a instance:
@ORACLE_HOME\sqlplus\admin\help\hlpbld.sql helpus.sql;