Visual Importer Oracle 12c

Have VI 9.2.12.4 running on server, using an Oracle DB repository.
VI is using Oracle 12c on app server to connect to our Oracle 19 databases.
Ora 12c has vulnerability and I need to remove, however VI Oracle ETL jobs begin to fail when I hide the 12c home and nothing I have tried (config, settings, registry) points VI to new 19c Oracle home.

Where is hidden bind in VI install to the old Oracle 12c home?
Do just have to backup VI home, deinstall, hide Oracle 12c home then reinstall VI?

I think the main issue here is configuring oracle client.

Bear in mind that 32 bit version of our ETL software use 32 bit oracle client and
64 bit 64 bit client

And since you are using Oracle repository you also need Oracle Ole DB provider.

Having multiple oracle client installed and multiple oracle homes complicates things a lot.

I would start from installing oracle client 19 on a fresh machine.   

Morning.
The VI is installed on a VM server and is 9.2.12.4 64bit.
Not able to move to another VM at this time.
I have both Ora 12c and 19c installed, but can not remove 12c yet due to VI jobs stop working.
Any other thoughts?
 

VI jobs stop working.

So what are the errors?

In a test I rename the Oracle 12c home with a "G:\apps\oracle\...\z_client_1"
Top grid of ETL job cannot connect and is blank with standard Ora TNS cannot connect error.
Run a >tnsping and oracle reports back no error under 30ms.
Hunted for every registry, .config, possible but VI top grid refuses to connect.
Rename the Oracle 12c home back to "G:\apps\oracle\...\client_1" and top grid populates and all is good.
19c is in OS %path% first, then 12c, but VI just not able to use it.

VI uses OleDB to connect to the repository.

I guess in your case it uses OleDB provider from 12c.
So when you rename the folder VI is unable to find OleDb provider 
Or if OleDb provider is in one of windows directories it is unable to find oracle client dll's
Please bear in mind you may also need to reboot the computer.

The reason I suggested to use separate PC first is to make sure that 19c client works correctly.
It can be any computer including your personal computer.

Than you can make a backup of VM, uninstall both clients and install 19c

Another alternative is to use SQL server express as repository