By default, Reports Server can only use Oracle Portal users to connect to Oracle Portal. It cannot use an ordinary userid, such as scott/tiger, unless you first assign appropriate privileges to its schema.
To assign the appropriate privileges to a schema other than the Oracle Portal schema, you must run the following script from SQL*Plus as an Oracle Portal user:
ORACLE_HOME/portal/admin/plsql/wor/rwgrant.sql
Once the script is loaded, it prompts you to enter the connection string for the new schema (for example, repapp/repapp@orcl). The script then assigns the appropriate privileges to this new schema. You can then specify this connection string in the destination element in the Reports Server configuration file to connect to Oracle Portal.