Allow overriding system value on update of audit columns

IBM does not intend to provide an additional solution to this request at this time, so it is being closed.

You can use OVERRIDING SYSTEM VALUE on the update statement and assign the row change timestamp column to its current value.

create table ga (
c1 int,
c2 timestamp not null generated always for each row on update as row change timestamp);
insert into ga (c1) values (1);

--The following will maintain the value of C2
update ga overriding system value
set c1 = 2, c2 = c2;

You will get an SQL0109 error if you specify OVERRIDING SYSTEM VALUES and you are changing a generated column.
In order to override the system value you must specify a value for the generated column.

Example:
create table mjatst.ga (c1 int, c2 timestamp Not null generated always For Each Row on Update as Row Change timestamp )
insert into mjatst.ga (c1) values(1)

The following will work and will insert the user specified value for C2.
update mjatst.ga overriding system value set c1 = 2, c2 = '2019-08-19-17.28.06.284821'

The following will generate a new value for C2:
update mjatst.ga overriding system value set c1 = 2

The following will return an error:
update mjatst.ga overriding system value set c1 = 2
SQL0109 OVERRIDING clause not allowed.

Being able to override the audit value would defeat the purpose of having the database do that update for you.