auto extend datafiles

Is the management of auto extend datafiles similar to the ones that are not?

I created one of the tablespace with the following syntax:

CREATE TABLESPACE "SIREPO" DATAFILE '/dsk01/oradata/edi/sirepo01.dbf' SIZE 100M AUTOEXTEND ON MAXSIZE 10000M extent management local uniform size 5M segment space management auto;

Now, the space is amost approaching to the max. Do I increase the space by adding a new datafile like the ones that are not auto extend, or is there a syntax that I can alter the datafile and set a new maxsize? If so, what is the syntax?

Thank you very much.