Restricted Session

 (1) Required Privileges

You must have the ALTER DATABASE system privilege.
To specify the RECOVER clause, you must also have the SYSDBA system privilege.

(2) Open the database -- READ ONLY / READ WRITE:

Example

The following statement opens the database in read-only mode:
ALTER DATABASE OPEN READ ONLY;

The following statement opens the database in read/write mode and clears the online redo logs:
ALTER DATABASE OPEN READ WRITE RESETLOGS;

(3) enable and disable a restricted session

alter system enable restricted session;

alter system disable restricted session;

to identify if the database is in that mode

select logins from v$instance;

In 10.2.0.3.0

ALTER SYSTEM QUIESCE RESTRICTED;