This first digit indicates the major database version and it describes the nature of release. Oracle releases a new release every four years on average.
For example: Oracle 9i (internet), Oracle 10g (grid), Oracle 11g (grid), Oracle 12c (cloud).
The second digit represents the software’s maintenance release number. Oracle releases the major update as maintenance release 1 and then follows up with a second maintenance release later in the software’s lifecycle. With maintenance releases, new features are introduced to database software.
For example: Oracle 12c release 1; Oracle 12c release 2.
Fusion Middleware Number is the third digit. This will be 0 for database software.
This fourth digit is called Component-Specific Release Number And a component release level is identified by the fourth digit. Depending on component patch sets or temporary releases, different components can have different numbers in this role.
Example: 12.1.0.1; 12.1.0.2; 12.2.1.1
A platform- specific release is identified by the fifth digit. This is usually a patch kit. this digit will be the same across all affected platforms when different platforms need the same patch package.
Example: GA release (initial release-no patch): 12.2.0.1.0
