EclipseLink features a number of enhancements for use with Oracle databases. These enhancements require classes from the Oracle JDBC driver JAR files to be visible to EclipseLink at runtime. If you place the JDBC driver JAR files in domain-dir/lib, the classes are not visible to GlassFish Server components, including EclipseLink.
If you are using an Oracle database, put JDBC driver JAR files in domain-dir/lib/ext instead. This ensures that the JDBC driver classes are visible to EclipseLink.
If you do not want to take advantage of Oracle-specific extensions from EclipseLink or you cannot put JDBC driver JAR files in domain-dir/lib/ext, set the eclipselink.target-database property to the value org.eclipse.persistence.platform.database.OraclePlatform. For more information about the eclipselink.target-database property, see Specifying the Database.