Trace a specific ORA- error

How to trace a specific ORA- error that is raised and can be reproduced?
We want to find the complete Oracle stack to understand the origin of this error.

For example, I want to understand why datapump expdp/impdp raises:
ORA-01422: exact fetch returns more than requested number of rows

This time, the alert file is not very helpful.

To determine the root cause, event 1422 can be set as follows:

connect /as sysdba 
alter system set events '1422 trace name ERRORSTACK level 3'; 

[…reproduce the issue…]

The event can be turned off again using:

connect /as sysdba

alter system set events '1422 trace name ERRORSTACK off';

In the event 1422 trace file, below sql query was causing error.

*** ACTION NAME:(Select sys_context into variable) 2017-01-27 14:15:24.257
*** MODULE NAME:(Trigger DDL_AUDIT) 2017-01-27 14:15:24.257
*** SERVICE NAME:(SYS$USERS) 2017-01-27 14:15:24.257
*** SESSION ID:(3265.22843) 2017-01-27 14:15:24.257
*** 2017-01-27 14:15:24.257
ksedmp: internal or fatal error
ORA-01422: exact fetch returns more than requested number of rows
Current SQL statement for this session:
SELECT UPPER(OSUSER), PROGRAM, MODULE, CLIENT_INFO FROM V$SESSION WHERE AUDSID = SYS_CONTEXT(‘userenv’, ‘SESSIONID’)

Of course, it’s easier to locate the target module if you have already instrumented your code with DBMS_APPLICATION_INFO.SET_MODULE and DBMS_APPLICATION_INFO.SET_ACTION;

In this case, the problem was due to SYS_CONTEXT(‘USERENV’,’SESSIONID’) returning 2 rows causing the ORA-01422 and subsequent datapump failure.

The workaround of this specific problem is to disable the Trigger DDL_AUDIT.
A solution is to modify the cursor or the statement in the trigger to retreive just one row, for example:
SELECT UPPER(OSUSER), PROGRAM, MODULE, CLIENT_INFO FROM V$SESSION
WHERE AUDSID = SYS_CONTEXT(‘userenv’, ‘SESSIONID’) and rownum=1;
Another solution is to trap error with an excveption clause.

 
Author: Vincent Fenoll, Oracle DBA Montreal

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