Tuesday Nov 10, 2015

Switch off "_rowsets_enabled" in Oracle Database 12c

Please find a recent update here:

 


 

Twitter is a good thing. I get alerted on things I haven't seen before. And sometimes some things are more than interesting.

This one is actually proven by Jonathan Lewis - and you can read all the details in Jonathan's blog post here:

There seems to be a realistic chance to get wrong query results displayed (regardless of using SQL*Plus or a JDBC or any other client - see the comment by Stefan Koehler below Jonathan's posting) because of the row sets feature in Oracle 12.1 allowing faster initial processing of query results.

You'll find this in the query information (marked in bold red):

Column Projection Information (identified by operation id):
-----------------------------------------------------------
 
   1 - "K"."KONTO_ID"[NUMBER,22]
   2 - "KWP"."WAEHRUNG"[VARCHAR2,20], "SV"."SONDERVERMOEGEN_ID"[NUMBER,22],
       "K"."KONTO_ID"[NUMBER,22]
   3 - "KP"."KONTO_FK"[NUMBER,22], "KWP"."WAEHRUNG"[VARCHAR2,20],
       "SV"."SONDERVERMOEGEN_ID"[NUMBER,22]
   4 - (#keys=1) "KP"."KONTO_FK"[NUMBER,22],
       "KP"."SONDERVERMOEGEN_FK"[NUMBER,22], "KWP"."WAEHRUNG"[VARCHAR2,20]
   5 - (rowset=256) "KP"."KONTOPOSITION_ID"[NUMBER,22],
       "KP"."SONDERVERMOEGEN_FK"[NUMBER,22], "KP"."KONTO_FK"[NUMBER,22]
   6 - (rowset=256) "KWP"."KONTOPOSITION_FK"[NUMBER,22],
       "KWP"."WAEHRUNG"[VARCHAR2,20]
   7 - "SV"."SONDERVERMOEGEN_ID"[NUMBER,22]
   8 - "K"."KONTO_ID"[NUMBER,22] 


Roy did some analysis yesterday as well (and now our Optimizer Support Experts look into this case to check whether any other wrong query result bugs are related to this topic). Because there are some open WRONG RESULTS bugs in this area, some of which were filed within the past week, we'd recommend to switch this feature off at the moment.  For instance these bugs are related to this misbehavior:

Recommendation - Updated (Nov 15, 2015)

Please read the update blog post here:


--Mike

Thursday Apr 17, 2014

Avoid Poor Performance and Wrong Results in 11.2.0.4

One of the best notes in MOS got refreshed last night for Oracle Database 11.2.0.4. It has not only information about performance bugs but also about the worst and meanest category of issues, wrong query result bugs. Those are the ones I call the "sleeping beauties" as you as a DBA usually won't recognize them. It is recognized at the application level when the result of a report is incorrect or instead of 4 rows just 3 rows get delivered in the output. Therefore you should be highly aware of those and add this note to your bookmarks.

MOS Note 1645862.1Things to Consider Before Upgrading to 11.2.0.4 to Avoid Poor Performance or Wrong Results

And in case you don't want to move to Oracle 11.2.0.4 but searching for information and known issues in Oracle 11.2.0.3 or Oracle 11.2.0.2 then please find the corresponding documents:

  • MOS Note: 1320966.1 Things to Consider Before Upgrading to 11.2.0.2.x to Avoid Poor Performance or Wrong Results
  • MOS Note: 1392633.1 Things to Consider Before Upgrading to 11.2.0.3 to Avoid Poor Performance or Wrong Results
-Mike
About

Mike Dietrich - Oracle Mike Dietrich
Master Product Manager - Database Upgrade & Migrations - Oracle

Based in Germany. Interlink between customers/partners and the Upgrade Development. Running workshops between Arctic and Antartica. Assisting customers in their reference projects onsite and remotely. Connect via:

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