As far as I can tell 'Response-time' has never been documented for optimization_goal since the option was introduced in V7 where the default was 'first-row'.

However it does appear that 'Response-time' is a synonym for 'First-row'... it's accepted by a V17 SET OPTION statement and it does get stored in the SYSOPTION table:

SET OPTION PUBLIC.Optimization_goal = 'Response-time';
SELECT * FROM SYS.SYSOPTIONS WHERE "option" = 'Optimization_goal';
user_name,option,setting
'PUBLIC','optimization_goal',Response-time

However, a subsequent ISQL SET statement displays 'First-row':

SET
optimization_goal   First-row

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In your case the value 'Response-time' was probably carried forward by the upgrade process... there's no "AI" component in the upgrade that can decide "No, they really don't want the old value, they really want to change it to something better"...

...you are your own AI :)

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For many (most?) applications, the application code DOES NOT receive and process (display) the first row of a large result set before the server has retrieved all the rows. Instead, the application does not display anything until the server has finished building the whole result set, and 'All-rows' is the value you want.

That's why 'All-rows' has been the default ever since Version 8.

See Tip: Choose the optimizer goal.

Searching within this forum is of help (and other search results might really anser your question):

Optimization_goal = 'Response-time'

IMVHO, this really just seems to be a synonym. You want to optimize the response time for the user waiting for the first results, right?

The equivalent optimization goal names.

Response-time == First-row

Resource-consumption == All-rows