The History Log can be activated to track changes in any table.

However, for the product structure you can also show changes using the Structure Journal page. 

@Björn Hultgren Thank you for your reply. It is exact what I need.

another question, see below IFSAPP is the owner of this change, wondering what exact activity that IFSAPP would do this? autojob? Thank you.

@ronhu That I unfortunately have no idea about. As you say, maybe you have some event that automatically sets the status to buildable?

@Björn Hultgren thank you.

There is the Structure Journal that shows these changes and which User performed the change.

@ConMan Thank you for your reply.