If you are seeing autocommits, it is usually because of an error in your logic. You probably have references set between uncommitted and committed entities.

The way to fix this is to ensure everything you need is committed, and references are removed to entities that shouldn’t be committed.

Autocommit can not be turned off.
 

https://docs.mendix.com/refguide/committing-objects#5-2-autocommit-and-associated-objects 

You cannot switch off autocommit: https://docs.mendix.com/refguide/committing-objects#5-2-autocommit-and-associated-objects

You might want to upvote this idea so that this feature might eventually be removed in a future version:

https://forum.mendix.com/link/ideas/1449

EDIT: upvote this idea: https://forum.mendix.com/link/ideas/650

Please all upvote https://forum.mendix.com/link/ideas/650. It has over a million votes and has been on Mendix’ Backlog for over three years and it is a useless pain in the ass.

Thank you all,

I saw this message in the console log:

Some autocommitted objects still existed on logout for session '200139333'.
Autocommitted objects are newly created objects which were not yet committed, but are inserted into the database because an associated object was committed.
Autocommitted objects should explicitly have been committed, please check your model and apply the necessary changes. The autocommitted objects have been deleted from the database to prevent database corruption.Number of autocommitted objects per type which still existed for this session:
- BackendModule.Application: 2 object(s).

What supposes this mean?