The documentation portal is undergoing maintenance. During this period, you can't create any new user credentials. If you do, you'll need to recreate the user credential after the maintenance period ends.
Run the history upgrade scripts to upgrade key history tables with new columns and to populate data in new columns that cannot contain null values. This step might create new tables and populate them with data.
The upgrade scripts are included in a zip file, for example, HRMS_HPY_UPGRADE_89To91.zip. If you customized any PeopleSoft module accelerator, you must update the "application changes" script to reflect the changes. For example, if you upgrade from PeopleSoft 8.9 to 9.1, the application changes script is HRMS_HPY_PS89_To_PS91_Upgrade_Appl_Changes.sql.