Hello, Ask Tom Team.

I have some many questions about Oracle RAC HA and Failover.

I was reading the info in below link and it help me a lot. But I still have some questions.
https://asktom.oracle.com/pls/apex/asktom.search?tag=failover-in-rac

I have Oracle RAC 18c (two nodes). All connection strings the app uses are the following:

--database service with DTP enabled to handle distributed transactions:
dbprod1_xa=
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = scanprod.local)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = dbprod1_xa)
)
)

grid@dbprodserver1:~$ srvctl config service -db dbprod -service dbprod1_xa
Service name: dbprod1_xa
Server pool:
Cardinality: 1
Service role: PRIMARY
Management policy: AUTOMATIC
DTP transaction: true
AQ HA notifications: false
Global: false
Commit Outcome: false
Failover type: SESSION
Failover method: BASIC
Failover retries: 2
Failover delay: 10
Failover restore: NONE
Connection Load Balancing Goal: LONG
Runtime Load Balancing Goal: NONE
TAF policy specification: NONE
Edition:
Pluggable database name:
Hub service:
Maximum lag time: ANY
SQL Translation Profile:
Retention: 86400 seconds
Replay Initiation Time: 300 seconds
Drain timeout:
Stop option:
Session State Consistency: DYNAMIC
GSM Flags: 0
Service is enabled
Preferred instances: dbprod1
Available instances: dbprod2
CSS critical: no
Service uses Java: false

--general connection string for the rest of connections that do not use distributed transactions.
dbprod =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = scanprod.local)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = dbprod) --> default database service (I know I have to change this)
)
)

1. What is an OCI client?
2. How Do I know if I have OCI or ODP.NET client?
3. I have DTP services (see tns entry above), which run on a preferred instance. Can these services be TAF enable despite they run on a preferred instance?
4. For the rest of the transactions (not distributed ones), is best practice that they point to a database service runnning on both instance (a created database service different from default)?
5. Can TAF, FAN and FCF be configured at the same time? What are the main differences between them?
6. What specific configuration Do I have to do to properly configure TAF? And How can I test it?
7. What specific configuration Do I have to do to properly configure FAN? And How can I test it?
8. What specific configuration Do I have to do to properly configure Application Continuity? And How can I test it?
9. Is enough to use simple tnsnames entries like the one above (I mean without additional parameters like LOAD_BALANCE, FAILOVER_MODE, RETRY_COUNT, RETRY_DELAY...)?
10. If my app is using a service running just on one instance, How to relocate this service to another instance without user interruption?
11. If my app is using a service running on both instances, How to shutdown one instance without user interruption?

Sorry for some many questions. I have read lots of Oracle documentation. I just want to make sure the best practice to configure my production environment.

Thanks in advanced.

Regards,