Tablespace & Datafile Autoextend

Hi,

I'm bit confused with the information shown in DB02. We are using SAP with Oracle 10g on HP-UX.

If I turn one data file autoextend off, the tablespace will change its' autotextend status from ON to OFF. But when I turn on the autoextend for that data file again, the tablespace autoextend won't change, it still shows OFF. What is the rationale behind this? How do I change the autoextent status for the table space? What is the purpose of tablespace autoextend?

Thanks