Dear,
Oracle 12C needs its specific JDBC driver that you could find at:
https://www.oracle.com/database/technologies/jdbc-drivers-12c-downloads.html
The ojdbc7.jar should be ok for your case.
The official documentation of Tomcat describes perfectly how to add the driver to the Tomcat installation directory: see the Introduction section. The instructions are for Oracle 8, 9 and 10 but are also valid for Oracle 12.
To update the Tomcat configuration you can follow the instructions at:
https://knowage-suite.readthedocs.io/en/7.1/installation-guide/manual-installation.html#connection-to-metadata-database
Where the <Resource> you should put in you server.xml file will be something like:
<Resource auth="Container"
driverClassName="oracle.jdbc.driver.OracleDriver" name="jdbc/knowage"
password="<password>" type="javax.sql.DataSource"
url="<JDBC URL>" username="<user name>"
maxWait="-1" maxTotal="10" maxIdle="1"
validationQuery="select 1 from dual" removeAbandoned="true"
removeAbandonedTimeout="3600" logAbandoned="true" testOnReturn="true"
testWhileIdle="true" timeBetweenEvictionRunsMillis="10000"
minEvictableIdleTimeMillis="60000" />
Where you have to configure at least the values of <password>, <username> and <JDBC URL>. The last placeholder will be something like :
jdbc:oracle:thin:@//<hostname>:<port>/<service name>
