ORA-12545 and ORA-12541

Every Oracle DBA knows how to check if a listener is running. lsnrctl status. If it’s down, start it. Problem solved, right? In a simple environment, yes. But in 2025, Oracle environments are rarely simple — they involve OCI networking layers, VCNs, Security Groups, firewalls, multiple listeners, RAC scan listeners, and PDB-specific services. The listener… Continue reading