When Oracle started offering support for the oracle db on RHEL, whenever there are performance issues and other issues, Oracle used to blame RHEL. So oracle DBAs are trained to go back Redhat for issues. Usually, these support issues bounce back and forth: Oracle blames Redhat, which says it’s an oracle issue. In the mean time, oracle support folks just buy sweet time. Then came Oracle enterprise linux: oracle supporting the whole stack, OS and databases. Which enterprise customer doesn’t want that. Not only that, many corporate customers of RHEL switched to Oracle Linux, as oracle charges way less for each installation.