ORA-31410: change set string is not an existing change set
Cause: Could not find an existing change set by this name.
Action: Check the spelling of the change set name. Call the procedure again, passing the correct change set name.

ORA-31405: cannot make changes while change set string is advancing
Cause: The change set is currently advancing. Change sources related to an advancing change set cannot be altered. Change tables related to the advancing change set cannot be created, altered or dropped. Some or all the parameters of the change set cannot be altered while the set is advancing.
Action: Wait until the change set has finished advancing, then reissue the command. If altering the change set, only the advance_enable parameter can be altered during an advance.

ORA-31399: Cannot contact LDAP server string at port number
Cause: The LDAP server specified could not be contacted. This can happen if the server is down or inaccessible.
Action: Contact the administrator of the LDAP server ////////////////////////// End of DBMS_LDAP & OiD messages

ORA-31229: DBMS_LDAP: invalid input parameter
Cause: An invalid argument has been passed by a PL/SQL module to a DBMS_LDAP subprogram
Action: Check the input argument to the DBMS_LDAP subprogram in PL/SQL module involving DBMS_LDAP.

ORA-31224: DBMS_LDAP: invalid LDAP session
Cause: An attempt was made by a PL/SQL module to use an LDAP session which is not valid and might have already been closed.
Action: Check the LDAP session handle in PL/SQL module involving DBMS_LDAP.

You must specify sid and serial identifing the session to kill. You can find these values querying the V$SESSION view:

SQL> SELECT sid, serial#, username from v$session;

Killing a session is very simple:

SQL> ALTER system KILL session ‘<sid,serial>’;

ORA-31411: change set string is referenced by a change table
Cause: The operation cannot be performed because the change set contains one or more change tables.
Action: You will need to drop the change table(s) first, then repeat the operation

ORA-31406: change source string is referenced by a change set
Cause: The operation cannot complete because this change source is referenced by one or more change sets.
Action: Drop the change sets first, then re-issue the command. May have to drop some change tables before the change sets are dropped.

ORA-31401: change source string is not an existing change source
Cause: The caller did not use the name of an existing change source. The name given does not match the name of any existing change source.
Action: Check the spelling of the change source name. Choose an existing change source.

ORA-31230: DBMS_LDAP: unable to dynamically allocate additional memory
Cause: An error occured during dynamic memory allocation from session heap.
Action: Verify that adequate memory resources are available.