In previous releases, I was not allowed to delete the active run of a Vivado project.
In Vivado 2015.3, I am allowed to delete the active run. However, if I delete the active Synthesis run, the active Implementation run is also deleted.
If I do this in a project with only one set of runs, the runs appear to be deleted, but they are still found with the get_runs command.
Additionally, if the project has Out-of-Context (OOC) runs for an IP core or another portion of the design, deleting the single set of project runs completely deletes the project runs (for example, synth_1 and impl_1) and one of the OOC runs becomes active.
In Vivado 2015.3, to prevent the active run being assigned to an OOC run or having runs in a partially deleted state, you should create a new run before deleting an active run if it is the only project run remaining.
In Vivado 2015.4, the behavior will be fixed as follows.