These fail on DB2 9.3 on zOS, see http://forums.activiti.org/content/db2-zos-support

UNI_BUSINESS_KEY varchar (255) not null generated always as (case when "BUSINESS_KEY_" is null then "ID_" else "BUSINESS_KEY_" end),
UNI_PROC_DEF_ID varchar (64) not null generated always as (case when "PROC_DEF_ID_" is null then "ID_" else "PROC_DEF_ID_" end),

As we already discussed we do not need the unique constraint on the database and could remove it as default (and maybe document how to introduce it yourself if you want to rely on it).