Why alter table column datatype is not allowed when one of the vertica nodes are down ?
With respect to current architecture of vertica, alter table column data type is not allowed. But how ever there is an enhance request which is being worked on for this issue
Changes cannot be propagated to the entire cluster so that is why you might not be able to make any changes while a node is down.
To workaround this create a new table with the desired definition, or bring the down node back online before.
Thanks Sruthi & Adrian for the update ...