Depending on the initial GeneXus version and to what target GeneXus version you are about to move, GeneXus does some conversion steps on your KB. In addition, you also need to follow certain steps.
Although guidelines are given below for upgrading a KB from one version to another consecutive version (for reference), it is also possible to upgrade a KB from one version to another major version without necessarily being consecutive. In fact, it is recommended to open the KB directly with the last released version of GeneXus.
Refer to Steps to build with GeneXus 18 a KB of GeneXus 17.
There is no KB conversion from 16 to 17.
Anyway, note that there may not be a way back. A KB that uses GeneXus Access Manager (GAM), once it is opened or built with GeneXus 17, cannot be built by GeneXus 16.
Furthermore, the information saved by some objects in GeneXus 17 (eg.: Query object) cannot be read accurately by GeneXus 16.
More information: GeneXus 17 Compatibility Section.
There is no KB conversion from 15 to 16.
More Information: GeneXus 16 Compatibility Section, GeneXus 16 is easy to adopt.
From GeneXus 9 on, you can open any KB with the latest released version of GeneXus, and all necessary conversion processes will be executed.
Although, as described above, you don't have to open your KB with a consecutive version number, it is recommended to check the following documentation:
Regardless of the conversion, it is advisable to perform an object navigation comparison.