This page helps edit the volume parameters.
Select a Volume
Select the volume and click on the volume details right hand pane.
Update the Volume Replication
Update the replication factor on the pop up that says “Edit Volume”
NOTE: The maximum replication factor supported is 3 and it is incremented or decremented sequentially. i.e. if current replication factor is 2, then the available options are 1 or 3. [assuming that the portworx cluster is of atleast 3 nodes]