db4o update behavior is regulated by Update Depth. Understanding Update Depth will help you to improve performance and avoid unnecessary memory usage.
When Update Depth is set to a big value on objects with a deep reference hierarchy it will cause each update on the top-level object to trigger updates on the lower-level objects, which can impose a huge performance penalty.
The following settings should be used with a special care and only with a good reason to do so:
Global deep update depth setting:
.NET:
configuration.UpdateDepth(Int32.MAX_VALUE);
This setting causes ALL objects in the database to be updated to the lowest possible level on each update.
Cascade on update:
.NET:
configuration.ObjectClass(typeof(Item)).CascadeOnUpdateDepth(true);
This setting will cause an update to the lowest level for Item class only. This can be unnecessary and therefore undesired in order to safe system resources.
For more detailed information, please, refer to Update Depth.