Why am I getting a 'sqlOpenResult' status='-28' error?
In most instances, the 'sqlOpenResult' status='-28' Cognos SQL error is generated due to invalid characters in a field. This applies to out of range dates as well.
The most common invalid character may be from a copy and paste action, where word formatting or characters are converted incorrectly, or not handled correctly, in PPM. While these characters are obvious and show up when editing the fields, they do NOT show up when you look at the values through the UI.
Valid date ranges are from 1950 through 2049 any years outside of this will error in Analytics. You will be able to enter a date outside of this range in the UI for custom fields, but it will generate an error in Analytics.
Thus, the best way of troubleshooting this is to limit the report to certain groupings, such as returning the data for only one project. Then, by narrowing down the project(s), you can edit each one in the UI, to bring up any invalid characters.