Can I upgrade directly from Datacom/DB version 12.0 to version 15.0 or 15.1?
For Datacom/DB you cannot upgrade directly from version 12.0 to 15.0 or 15.1.
The Datacom/DB 15.0/15.1 upgrade process can only upgrade a 14.0 Datacom/DB MUF.
You will need to first upgrade from version 12.0 to 14.0 and then upgrade from version 14.0 to either 15.0 or 15.1.
The upgrade to 15.0/15.1 has been simplified and is now called an Active Multi-User Facility Upgrade
To upgrade to 14.0 see section Upgrade Installation Phase in the Installation Guide for z/OS 14.02 and the README RI37761.
To upgrade to 15.0 see How to Perform an Active Multi-User Facility Upgrade in DocOps and the README RI67375.
To upgrade to 15.1 see How to Perform an Active Multi-User Facility Upgrade in DocOps and the README RI86635.