as i know silverstripe 2.3.3 doesn´t support so far "locking"/mutual exclusion of pages/dataobjects if they are edited at the moment by another user;
for better understanding just think of the following user scenario:

1.) User A opens a page in the sitetree and edits it but has not saved it yet
2.) User B opens the same page and edits it and also saves it
3.) User A saves now his changes and so he is overiding the changes of user B, so the changes of user B are lost and user A and user B have not got any messages that this happened;

so my question is, if anyone has already extended SS or implemented an enhancement which ensures mutual exclusion in SS? advice to implement this is also welcome;