SQL & PL/SQL

Given the following example

cursor test_cursor is
 select * 
 from authors;

open test_cursor;

if (test_cursor%rowcount = 0) then
 raise no_data;
else
	close test_cursor;
	for test_cursor_rec in test_cursor
	loop
		update authors
		set id="21"
		commit;
	end loop
end if;

The above code example, selects everything into a cursor and loops through the cursor to update rows that are in the authors table. This is the same data that is on the cursor. I have been getting "snapshot too old" errors and reading about this error i concluded that the commit statement is causing this as i am making changes to the data which the cursor is using.

What is the alternative way to do this to avoid the "snapshot too old" errrors. ?

Thanks