Its difficult to answer this question specifically without knowledge of how both AdvantageGen and your java application access the database.
However generally speaking, you need to be very careful when attempting to share a database between multiple applications. When applications are written, the author usually has in mind whether or not the application is to have exclusive access to the database in question or not. When an application expects to have exclusive access then often it can take additional liberties when it comes to caching data, and optimistic locking for the purposes of optimisation. Attempting to share databases where this is the case, can undermine the existing application.
So sorry no easy answer. You need detailed knoweldge of the data access of both applciations.
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