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.
A PowerCenter workflow can write to NRDB target types ADABAS, IMS, SEQ, TAPE, and VSAM. For these target types, it is possible to execute INSERT SQL to insert rows with hard-coded data values into the output table.