-- Current sessions:
SELECT USERNAME, count(*) as connections FROM v$session GROUP BY USERNAME;
-- Limitations:
SELECT a.USERNAME, b.PROFILE, b.RESOURCE_NAME, b.LIMIT
FROM DBA_USERS a, DBA_PROFILEs b
WHERE a.PROFILE = b.PROFILE AND b.RESOURCE_NAME = 'SESSIONS_PER_USER';
-- Change limitation:
ALTER PROFILE my_profile LIMIT SESSIONS_PER_USER 10;