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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.

using NOLOCK hint

Use NOLOCK hint to avoid block – this is what I have often heard/see in many forums I participate in, during local user group events and meetings. I have always advised that its not that good idea to use hints, as it may cause data corruption and blocking. And anyways, there are many things that [...]

Test Data

The UKOUG conference is over for another year – but it has left me with plenty to do and lots of things to investigate. Here’s just one little point that I picked up during one of the 10 minute “Oak Talks” that members of the Oak Table Network were doing in the lunch breaks.

There is a fairly well-known strategy for generating a list of numbers by using a “select from dual … connect by …” query, but I hadn’t realised that there were two ways of using it. The code I’ve usually used is this:

Oracle Core

As Martin I had a pleasure to “unofficially” review Jonathan’s latest book, Oracle Core. It was my first experience in the area of printed content. If you want to know little bit more how the process went, my opinion on the book and what to expect from it – I’ll try to cover these points here.

The cause for and against the Exadata simulator

I am on my way back from the best UKOUG conference I ever attended, unfortunately a lot earlier than planned. Before I start forgetting all these great moments it is time to write them up. To make use of James Morle’s words: if you weren’t there, you lose. I couldn’t agree more!

Will the Single Box System make a Comeback?

For about 12 months now I’ve been saying to people(*) that I think the single box server is going to make a comeback and nearly all businesses won’t need the awful complexity that comes with the current clustered/exadata/RAC/SAN solutions.

Now, this blog post is more a line-in-the-sand and not a well researched or even thought out white paper – so forgive me the obvious mistakes that everyone makes when they make a first draft of their argument and before they check their basic facts, it’s the principle that I want to lay down.

Projection Pushdown bug in

There’s a bug in related to projection pushdown that seems to be influenced by the setting of STATISTICS_LEVEL.

Having taken the time to distill a test case from a real world issue (commenting out columns and logic and bringing view definitions inline etc – original query had no reference to DUAL), turns out it’s very simple to reproduce:

sundiag Exadata

Exadata is greatest but it's not right out of Utopia so expect problems. One of the problems which sometimes arise are related to physical disks. But as usual Oracle has got some nifty and pertinent tools for the diagnostics. Sundiag is one such tool. Sundiag is used to diagnose the problems in the disks in Exadata. This script is run as the root user.

Sundiag is run by following command as root:

UKOUG Annual Conference 2011

Having been involved with the UKOUG for more than 10 years now, one of the things that is so nice about returning to the annual UKOUG conference is the sheer number of familiar faces.

It also is a great place to hear about other people’s experiences and an opportunity to broaden your horizons.

Sadly due to my youngest daughter’s terrible timing of being born at this time of the year, I had to miss the fabulous Oaktable Sunday and be at her 4th birthday party instead. Thanks to everyone who told me how good it was. While this did not exactly help, I’m glad others had fun.

Table Functions And Join Cardinality Estimates

If you consider the usage of Table Functions then you should be aware of some limitations to the optimizer calculations, in particular when considering a join between a Table Function and other row sources.

Day 6: The Twelve Days of SQL: The execution plan is a tree

On the sixth day of Christmas, my true love gave to me Six geese a-laying. Day 6: The execution plan is a tree (Day 5: The query cost is only an estimate)(Day 7: EXPLAIN PLAN lies) An execution plan is a tree. This is not very obvious from the listing of DBMS_XPLAN or EXPLAIN PLAN but [...]

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