How to Synchronize two tables both way between two different database servers?

Question

I am currently developing an architecture as follows

1. Admin User will create credentials for other users through an web application(Say App1). Same will be stored in a oracle 12C database(Say DB1)
2. Ordinary user will connect to a different system(Say app2) with that credential
3. That system will use Radius Server to authenticate(Simply pass the entered credentials to Radius Server).
4. Radius Server(Say RS1) will use DB1 database to authenticate user Same has been done and working fine.

Now I want the following thing

1. Configure another Radius Server(Say RS2) which use another Oracle database (Say DB2). DB2 and DB1 must be on a different server to prevent single point failure.
2. Shifting all request from RS1 to RS2 whenever RS1 is not available
3. for this I need DB1 and DB2 are real-time synchronized(both way). IF DB2 is not available for some time, all the updates done on DB1 must be synced when DB2 is available vice versa.

Can anyone let me how to achieve point 3 only? Please note, only one table needs to be synchronized. Only DML operations are there

Answer 1

You requirement is bit similar to High Availability of your DB server. please look into the following link https://docs.oracle.com/cd/B28359_01/server.111/b28281/architectures.htm#i1008361 http://www.oracle.com/technetwork/database/availability/index.html

Ideally, High availability is configured with One Master Node(server) and two slaves (among them one at least should be active stage)

Now, if the master is down, the active slave become Master and passive one will be active.

Later when initial master is recovered, it will be acted as passive slave.

All the servers would be in sync (periodically or with some pre-defined trigger points)