Improve the error messages - eg tell us WHICH records had Key Violations
Many of the error messages could be more informative. Those that tell us 'it was not possible to xxxx nn records' could provide information in a table about which records had the problem - like you get with type conversion errors on an import.
Krzysztof Żelechowski commented
To make matters worse, the description of Common errors when you run an append query  is incomplete: Key violations may be triggered by relationships too.
 <URL: https://support.office.com/en-us/article/common-errors-when-you-run-an-append-query-26eecd3b-cbea-45c1-80c4-f5bb50a9ccfa >
From the programming/maintenance side, this is a no-brainer. Of course we need this' it would be nice to have some meta data to go with it.
John Partyka commented
I'm using my last vote on this one, plus the comment added by Mark Burns. I've wasted too many hours (probably months by now) on trying to find that one bogus row out of 50,000+ others in my input data.
Mark Burns commented
I enthusiastically endorse this idea, but have no votes remaining to use for it.
There are few things that Access does to frustrate you _more_ than to toss up that generic "xxx records not imported due to yyy type conversion errors, and zzz unique constraint violations..." etc.,. error message during a data import task.
Sorry, but THAT IS JUST NOT ADEQUATELY USEFUL INFORMATION! We NEED to know PARTICULARS about WHAT record(s) an/or data failed to meet WHAT constraints! What records had type conversion failures on what values into what target fields?! When we get THIS data we then will have ACTIONABLE error correcting steps. Until then, it's a guessing game as to what isn't working.
I would wish for you Access Dev Team folks to be under the gun to crank out a report for a meeting in 30 minutes, and with 10 minutes left to import a table and crank out a needed chart or report for the meeting, to be tossed into this particular error message heaven. Then you will begin to understand our frustration with this inadequate error messaging.