Find existing sessions to DB using this query: SELECT s . inst_id , s . sid , s . serial #, p . spid , s . username , s . program FROM gv $ session s JOIN gv $ process p ON p . addr = s . paddr AND p . inst_id = s . inst_id WHERE s . type != 'BACKGROUND' ; you'll see something like below. Then, run below query with values extracted from above results. ALTER SYSTEM KILL SESSION ' , ' ; Ex: ALTER SYSTEM KILL SESSION '93,943';