Workaround
Run the attached permissions script to grant permissions to the user on v$px_session. This script is compatible with all support Oracle versions. Users may require being logged in to download this script. The username (&&USER_NAME) must be included when running this script.
An updated check permissions script has also been attached to this knowledgebase article.
Status
This issue was logged as defect FOG-5823 and has the permissions script and installer wizard have been fixed in the 6.3.0.20 Oracle and higher cartridges.
IMPORTANT: After upgrading to the 6.3.0.20 or higher release from any lower cartridge version, revalidate all of the connections to the Oracle agents. This step will apply the updated permissions to the user accounts used by the Oracle agents. Knowledgebase article
4235896 describes how to revalidate the Oracle agent connections.
NOTE: As there are seem to be ten concurrently used to validate agents, Support recommends validating agents in small groups of ten or less. This will reduce the change of timeouts, particularly if other users might be making changes to agents in the system at same time as the validation of agents are queued up.
Defect FOG-6313 has been logged to fix the Oracle agent installer to revalidate and apply the updated permissions during the upgrade wizard process. This will be fixed in a future release of the Oracle cartridge.