The Introduction to Oracle Database includes a brief history on some of the key innovations introduced with each major release of Oracle Database.
Oracle Corporation releases Critical Patch Updates (CPUs) or Security Patch Updates (SPUs) and Security Alerts to close security vulnerabilities. These releases are issued quarterly; some of these releases have updates issued prior to the next quarterly release.
A 2016 Gartner report claimed to show Oracle holding #1 RDBMS market share worldwide based on the revenue share ahead of its four closest competitors – Microsoft, IBM, SAP and Teradata .[verification needed][clarification needed]
In the global database market, Oracle and Microsoft still maintain the dominant situation. Recently, they have followed the trend of artificial intelligence and launched autonomous Oracle database service. In addition, Oracle's long planned China database center will be launched this week, and plans to launch autonomous transaction processing services. 
In the market for relational databases, Oracle Database competes against commercial products such as IBM's DB2 UDB and Microsoft SQL Server. Oracle and IBM tend to battle for the mid-range database market on Unix and Linux platforms, while Microsoft dominates the mid-range database market on Microsoft Windows platforms. However, since they share many of the same customers, Oracle and IBM tend to support each other's products in many middleware and application categories (for example: WebSphere, PeopleSoft, and Siebel Systems CRM), and IBM's hardware divisions work closely with Oracle on performance-optimizing server-technologies (for example, Linux on IBM Z). Niche commercial competitors include Teradata (in data warehousing and business intelligence), Software AG's ADABAS, Sybase, and IBM's Informix, among many others.
Increasingly, the Oracle database products compete against such open-source software relational and non-relational database systems as PostgreSQL, MongoDB, Couchbase, Neo4j and others. Oracle acquired Innobase, supplier of the InnoDB codebase to MySQL, in part to compete better against open source alternatives, and acquired Sun Microsystems, owner of MySQL, in 2010. Database products licensed as open-source are, by the legal terms of the Open Source Definition, free to distribute and free of royalty or other licensing fees.