I got a very helpful answer from the Cloudera Support and it did the trick:
Look for "Hive Metastore Server Advanced Configuration Snippet (Safety Valve) for hive-site.xml" in the Hive configuration, press (+) [Plus button] and specify the following:
in the "Name" field: javax.jdo.option.ConnectionURL
in the "Value" field: jdbc:oracle:thin:@(DESCRIPTION=(LOAD_BALANCE=off)(FAILOVER=on)(CONNECT_TIMEOUT=3)(RETRY_COUNT=3)(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=oracle-server1)(PORT=1521))(ADDRESS=(PROTOCOL=TCP)(HOST=oracle-server2)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=ora_service_name.ora_domain_name)))
NOTE: You will have to change the connection string correspondingly - I just showed an example of the failover-able (primary + standby DBs) Oracle TNS connection string.
The same trick can be used for "Sentry", but the corresponding parameter name is: "sentry.store.jdbc.url"