A dot (.) patch level such as 923.21 indicates that a total of 944 patches have been applied to the pristine source. In the case of CDH3 (hadoop-0.20.2+923.21), 923 patches were applied during the beta phase before the Stable CDH 3u0 release, and 21 more patches were applied after Cloudera created a new branch for the CDH 3u0 release. Once CDH 3u0 was released, further patches at CDH 3u1, u2 and so on increment the dot patch level.

In the case of hadoop-0.23.0 (CDH 4), the main patch level (161 at beta 1) will increase with each beta release. Dot patch levels will not be used until the stable release occurs.

This dot notation is necessary for package managers like apt and yum to correctly choose upgrades based on the repository you are tracking. Package managers interpret version numbers with more segments as newer; that is, 923.21 > 923. However, the number of segments is ignored if the first segment is greater; such as 76.2 < 77. Note that CDH 1 used a different syntax, which is now deprecated.