My boss was attempting to install Oracle 12c on an EC2 instance running Linux but it was failing mysteriously, so he handed it off to me, the Database Guy (tm). The logs reported this error:
"ORA-21561: OID generation failed"
Wha'? After some head scratching and googling I learned this can happen if the host name you’re installing on is not resolvable. Boss said he did not enable DNS on the VPC (Virtual Private Cloud - an Amazon thing). I took a look at the Oracle install script (that was apparently generated by Amazon) and found that it’s getting the host name via a curl call, to retrieve meta-data Amazon provides for your EC2 instance: something like ORACLE_HOSTNAME=`curl -s http://xxx.xxx.xxx.xxx/latest/meta-data/local-hostname/`
One option would be to get rid of that call and set ORACLE_HOSTNAME to localhost. Another would be to add the EC2 host to /etc/hosts. I opted for the latter (I wasn’t convinced that was the only place that needed the host) then installation worked. (Yay!)