Oracle is losing market share consistently and irreversibly for the last 4-5 yrs. It is not due to migration to open source RDBMS, but also due to the fact that now there are many alternatives to RDBMS for data storage. Until about 10-15 yrs back, if the application has to store data, then RDBMS was the only choice. I have seen Oracle used to store news text and for nothing else in that app. For searches inside the news text, 3rd party app was used. Now such applications use Solar Lucene or Mongodb type of app. Cassandra is used for high write intensive apps. If someone publishes cases of Oracle being used for new projects, I bet it will be shockingly low. Same is true for DB2 and even SQLServer. In general RDBMS is no longer used for every application where they are not the right fit.
