Make database to be read only

How can I make database to be read only?
Answer:
To make database to be read only, you can use the Enterprise Manager or the sp_dboption system stored procedure.For example, to make the pubs database to be read only, you can use the following statement:
Scripts:
EXEC sp_dboption 'pubs', 'read only', 'TRUE'
To make it online again, follow the below script
EXEC sp_dboption 'pubs', 'read only', 'FALSE'