What Oracle Version Digit Mean

The first digit is the most general identifier. It represents a major new version of the software that contains significant new functionality.
Database Maintenance Release Number

The second digit represents a maintenance release level. Some new features may also be included.
Application Server Release Number

The third digit reflects the release level of the Oracle Application Server (OracleAS).
Component-Specific Release Number

The fourth digit identifies a release level specific to a component. Different components can have different numbers in this position depending upon, for example, component patch sets or interim releases.
Platform-Specific Release Number

The fifth digit identifies a platform-specific release. Usually this is a patch set. When different platforms require the equivalent patch set, this digit will be the same across the affected platforms.

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Osama Mustafa