Oracle version numbers can be confusing at first. The RDBMS uses a four-number version number—for example, 220.127.116.11. In this number:
The first digit refers to the major release of the RDBMS.
The second digit refers to a minor release of the RDBMS. The first two digits together define a release level whose functionality has been defined and documented by Oracle Corporation.
The third digit refers to a code release by the base engineering group for the release level.
The fourth digit defines a patch set of specific cumulative patches to the code release.
The version number referenced above, 18.104.22.168, is the second patch set to the fourth code release of the 8.0 functionality (see Figure 1.2).
Some Oracle releases (most notably those for Unix platforms) use a five-digit numbering system, but the fifth digit is almost always or 1.