Postgres Plus Advanced Server (PPAS) is a licensed version of PostgreSQL owned by EnterpriseDB. You need to buy a support contract to use this software (although there is a 45 day trial period).
The component you are talking about is xDB Replication Server, which is part of the PPAS product or can be licensed separately for use with community versions of PostgreSQL.
xDB Replication server is trigger based (on both the Oracle and the PostgreSQL side). It can handle asynchronous master/slave or multi-master replication.
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