What is real datafile size?

Hi, When I read Oracle8 Server Administrator's Guide(p9-6), I am not sure for the real datafile size in following command:

Alter Tablespace Users Add Datafile 'filename2' size 10M

        AutoExtend ON
        NEXT 512K
        MAXSIZE 250M

[1] It seems the filename2 size can reach to 250M. What is the use of
item 'size 10M'?
[2] Does filename2 start to extend after it reach size 10M or from
begin?
[3] What is the difference of above command with the following one:

      Alter Tablespace User Add Datefile 'filename2' size 250M

Any help will be appreciated!

Sheng Jin Received on Fri Apr 14 2000 - 00:00:00 CDT