ORA-00029 Session is not a user session

Cause: The session ID specified in an ALTER SYSTEM KILL SESSION command was not a user session (for example, recursive, etc.). Action: Retry with a user session ID.

ORA-00028 Your session has been killed

Cause: A privileged user has killed your session and you are no longer logged on to the database. Action: Login again if you wish to continue working.

ORA-00027 Cannot kill current session

Cause: Attempted to use ALTER SYSTEM KILL SESSION to kill the current session. Action: None.

ORA-00026 Missing or invalid session ID

Cause: Missing or invalid session ID string for ALTER SYSTEM KILL SESSION. Action: Retry with a valid session ID.

ORA-00025 Failed to allocate %s

Cause: Out of memory. Action: Restart with larger sga heap.

ORA-00024 Logins from more than one process not allowed in single-process mode

Cause: Trying to login more than once from different processes for ORACLE started in single-process mode. Action: Log off from the other process.

ORA-00023 Session references process private memory; cannot detach session

Cause: An attempt was made to detach the current session when it contains references to process private memory. Action: A session may contain references to process memory (PGA) if it has an open network connection, a very large context area, or operating system privileges. To allow the detach, it may be necessary to close the…

ORA-00022 Invalid session ID; access denied

Cause: Either the session specified does not exist or the caller does not have the privilege to access it. Action: Specify a valid session ID that you have privilege to access, that is either you own it or you have the CHANGE_USER privilege.