To upgrade from Datacom/AD 15.0 to 15.1 , first install the Datacom/AD 15.1 software then perform an Active MUF Upgrade from 15.0 to 15.1.
You must have completed the process of upgrading your Datacom Datadictionary Version to 15.0 before performing a 15.0 to 15.1 active MUF upgrade.
The 15.0 Datacom/AD Multi-User Facility (MUF) should show these messages during startup:
DB00915I - CXX DBID 2 DATA-DICT DEFINITION VERSION 15.0 CHANGE LEVEL 0
DB00915I - CXX DBID 15 DDD-DATABASE DEFINITION VERSION 15.0 CHANGE LEVEL 0
Release : 15.1
Component : Datacom/AD
CAI.HLQ.INSTJCL
CAI.CHLQ.CUSLIB
CAI.CHLQ.CUSMAC
CAI.CHLQ.CUSPROC
After the upgrade to version 15.1 the MUF startup still shows version 15.0 in the DB00915I messages since there is no base upgrade for DATA-DICT or DDD-DATABASE when upgrading from version 15.0 to 15.1.
Note that the DB00915I message for CASYSTEMTABLES can show 14.0 or 15.0 ( not 15.1).
See the Datacom/AD documentation section Installing.