Build configuration or template uuid. If specified, TeamCity uses this uuid to identify the entity. If uuid is not specified, then id is used instead.
Uuid must be unique across all entities on the server.
If uuid changes, TeamCity considers it to be a new entity. For a build configuration it means that previously created history of builds won't be available until the previous value of uuid is restored.
If uuid is not specified then the builds history is associated with a build configuration with help of id. As a result a change of the id will make builds history unavailable until the previous value of id is restored.