Data Loading and Entity Modification

Hello,

I have a question about the entity engine in OFBiz, mainly pertaining to how
changes to "entitymodel.xml" and seed data are handled when there is already
data in the entity.

I've done some searches and experimentation on my own to try and determine
this but came up inconclusive results:

1) If more seed data needs to be loaded after the system is already in
production, will the seed data loader skip loading records which are already
in the entity, and only add the new ones? If not, what is the recommended
way to add the new data to the entity if not using the seed data loading
functionality?

2) If a schema change is required (i.e. data type change, column
addition/removal) how do you go about doing this on a system already in
production (which will have existing data), using the entity engine? If it
can't be done with just the entity engine and would require an external DB
tool to do so, how do you ensure that OFBiz's "entitymodel" is back in sync
with the new DB schema?

Thanks!