But we must save subdata. This is not a "word like document" which can saved at once, in a transaction. When a product edited, we must protect it from other user's edit. But it's subdata must be posted/commited to the DB, for example shipping, article quantity changes, vouchers, etc.
So folks can make changes to the attributes of a Product, Offer, etc while it is being changed in ways they can not see?
They are not linked closely. Other people also could give new transport areas. And they must read them.
And no, Product and Offer elements don't editable for more people at once.
Or do they get a read only view that changes as the 'locking' user makes edits?
Yes, and they can add new lines.
To be clear you are trying to come up with a solution that allows your application to run against different databases(Firebird, SQL Server, Postgres, etc?), using a single code base, correct?
Yes, absulately right.
We have 3 choices:
1.) A second connection with locking transaction (we lock other resources)
2.) An advisory locks.
3.) A multi-DB solution - if we can identify the current sessions in 99.99% (except summer/winter or other hour problem and perfect similarity of timestamps).