On my test server I was installing a custom application which uses the Oracle Database as Backend. However My installation failed and I have contacted their support team. However my issue is that now even when I am trying to connect with plain SQL Plus into the Oracle Database I am getting this: ORA-01034: ORACLE not available ORA-27101: shared memory realm does not exist Now I did the basic troubleshooting and restarted Oracle service to make sure it is mounted correctly. But this is refusing to go away. It is interesting because there seems to be no issue with starting and shutting down oracle. Any ideas?