What is Demo Oracle?
Oracle Demonstration Services provides demonstration environments (based on availability) to qualified Oracle PartnerNetwork (OPN) members. Demonstration environments are offered for demonstration and training purposes on Oracle's technology, applications, and cloud products
You may create your own, just read the blog
Oracle DBA and development articles, scripts, HOWTOs and forums (8i, 9i, 10g, 11g, 12c, 13c, 18c, 19c, 21c)
