Oracle Solution for Error ora-29393

ORA-29393: user string does not exist or is not logged on

What triggered the Error:

invalid user name was specified as argument to procedure SET_INITIAL_CONSUMER_GROUP of package DBMS_RESOURCE_MANAGER or SWITCH_CONSUMER_GROUP_FOR_USER of package DBMS_SYSTEM or the specified user was not logged on.

What should we do to fix it:

ecify a valid user name.