Considerations for pluggable databases and container databases
When you are capturing data from a pluggable database, Oracle XStream requires all XStream components to be created in the root container database.
When you create an instance that is intended to replicate data from tables in a pluggable database, ensure that the log processing database is the root container database of the pluggable database. Information that is associated with Oracle XStream capture initialization points is also generated in the common root container database. As such, if you happen to create multiple CDC Replication instances to replicate data from multiple pluggable databases that are associated with the same root container database, then all instances could share all the initialization points from the container database across all subscriptions and all CDC Replication instances.