Starts a run: the fence, the snapshot and the plan, as the first three units.
Refuses when a run is already live, because two cursors over one schema is the
one failure this whole file exists to prevent.
maint_was is read here, in JS, BEFORE any PHP runs -- so the value restored at
the end is the value that was true before the fence went up, and it is durable
rather than session state.
Starts a run: the fence, the snapshot and the plan, as the first three units.
Refuses when a run is already live, because two cursors over one schema is the one failure this whole file exists to prevent.
maint_wasis read here, in JS, BEFORE any PHP runs -- so the value restored at the end is the value that was true before the fence went up, and it is durable rather than session state.