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Database Feed

Oracle Database, Oracle 10g, Oracle 11g, Oracle XE, Oracle RAC, Oracle Instant Client, Oracle Data Guard and Oracle Exadata resources, news, and support articles.

Wrong results with 'hash group by' aggregation on

If you are running in your production environment check document [ID 4604970.8] on Oracle support site.

This week colleague noticed that query, he wanted to use for some reports, returns different results than he expected. He made some additional checks using Microsof Excel and confirmed that something is wrong. He was getting incorrect results.

My first suspicion was that probably something is wrong with query or maybe logical corruption happened.

Example of the queries (I’ve changed names of the table/columns):

Bitmap Indexes and Not Equal Part II (Sheep)

An excellent comment/question by mdinh made me realise my demos in Part I might be a little extreme in returning 0 rows and perhaps give the false impression that Not Equal conditions are only considered or applicable if no rows are returned. This is not the case and with the bitmap index now considered with Not [...]

Tom Kyte in Dayton

Tom Kyte of is coming to Dayton on July 14!

This is crazy-big for Dayton. Tom is one of the most amazing Oracle experts out there, with an immense knowledge of Oracle and a gift for getting straight to the heart of questions and problems; you really need to see him in action.

Inside Grid Control

Lors de mon activité de consultant, et suite à un bug qui n'affiche pas correctement le nombre de CPU (OMS, agent et linux x86_64), je me suis intéressé à la manière dont Oracle Enterprise Manager Grid Control (OEM GC) récupérait les informations de mémoire et de cpu sur les différents hôtes surveillés par ce dernier.

Dealing with multiple tnsnames.ora files on a windows client

Part 1

A common problem found at many sites is having Windows clients with several Oracle products installed.

If each installation uses its own tnsnames.ora file to identify the database services that the client can connect to, then users often experience connection issues. 

If a new database service is added, it’s not always clear which tnsnames.ora file(s) need to be updated.

How Many Ways to Solve this SQL Problem?

July 6, 2011 Since there were so many unique solutions to the last blog article that posed a SQL challenge, I thought that I would try another blog article that asks a similar type of question.  Assume that someone showed you the following output:  C2   D --- --- 100   0 150  50 200  50 201   1 [...]


A question about partitioning came up on OTN a few days ago – but the really interesting part of the thread was about the choice of indexes, and how the choice of partitioning, combined with the data patterns, could make a big difference to the choice of indexes. I think the comments I made about indexes are worth seeing, so I’ve linked to the thread.

RAC hack!

In other words – FREE STUFF!!!

Riyaj Shamsudeen does a free RAC hacking session on 12 July!

He will demonstrate how the LMS background process works, with the help of OS tracing tools like truss and DTrace.

Sign up here!


Important Statistics & Wait Events on Exadata

With this posting, I’d like to highlight the most important Statistics & Wait Events on Exadata that a DBA needs to be familiar with in my view. We start with Statistics, retrievable from v$sysstat, for example. For Exadata, we have introduced 43 new Statistics, that start all with ‘cell%’:

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