Test Automation - Initializing database state

I have a situation I'm hoping you can provide some insight into. I am thinking about test automation (JAVA) for a system that goes through various stages of processing and has a large Oracle database (1000+ tables) at its core.

E.g. process 1 - Run Process1 -> Find file with customer details -> load details to staging tables in database. process 2 - Vet customer details -> Run Process2 -> Customer details found in staging tables will be moved to proper tables.

Now from an automation point of view I need to re-initialize the database state each time before I run a test, but the problem is that the database instance will be shared by some others. Without getting into the why we don't have a separate database instance, does anyone know how to contain the state? So for example imagine a database with a table Customer, that contains a column FirstName.

Before test run: FirstName contains the data 'Peter', 'Paul',

After test run: FirstName contains the data 'Peter', 'Paul', 'Jack', 'Amy' Before next test run: What is an effective way to bring the database state back to how it was before the last test run i.e. the data contained should be 'Peter', 'Paul' again.

I have seen DBUnit but my understanding is that whilst you can initialize the state with your own data before a test run, it will also clear all data before a test run. The problem is that I don't want to clear all data before a test run, but just that data that was introduced as part of the last test run.

I hope that was clear :) Thanks!