Query not in code, but has vaguely known WHERE condition

I found a strange SQL in our database, causing Library Cache and Cursor Sharing fun of all kinds, but no need to elaborate on that. The database is a jungle of dynamic SQL and parsing storms, so we had to enable CURSOR_SHARING=SIMILAR to work at all. No value in ranting on that.

What I need to do is, to find where it comes from, to start investigating the case.

The SQL text is like that:

SELECT :"SYS_B_0"
FROM DUAL
WHERE a.div_id = b.div_id

AND a.entity_id = b.entity_id 
AND a.attribute_id = :"SYS_B_1" 
AND a.other_id = :"SYS_B_2" 

We can see it being a top consumer or waiter in currently running / active sessions and ASH, but it never shows up in AWR. For sure, that's not one of ours, even when ignoring the fact that it does not make much sense for itself. All I recognise is the WHERE condition - it may match some of our MERGE ON clauses.

So my questions:

1. How does the DB come to creating this kind of SQL text?
2. What's the use of it, the mechanism behind?
3. How can I find out where it is triggered?

Thank you all in advance!
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Freundliche Grüße / Best regards

Martin Klier
Performing Databases GmbH
Oracle ACE

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http://www.freelists.org/webpage/oracle-l Received on Mon Jan 26 2015 - 13:53:53 CET