This cloud wiki setting specifies the major version of the database, as set when the database was created or last migrated. Across major versions, the database may change in ways that are incompatible with other server versions.
Modifying this setting will probably make your server unstable, runs the risk of data loss, and other unsavory things -- you should use the "cloud-wiki migrate" command if you want to move from one version to another.
You should reboot the server after changing this setting.
This node is a part of the cloud wiki manual.