[Pmwiki-users] What is happening when several people try to edit the same page at the same time.

[wda]

Hello
Some user of my wiki have experienced problem because they were two 
editing the same page and the last press save loose its modifications (I 
do not have the details of the error or exactly what happen). What 
should have happened?
Is there a way to prevent a user from editing a page when this page is 
currently being edited?
Thank
Axl