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Testing

Submitted by Jonathan Lewis on Wed, 2010-06-02 20:20

The old chestnut of “optimal block size” came up on OTN again a few weeks ago, with someone asking for advice on how to do some testing to decide on the optimal block size for a database. The correct answer to this question is you don’t: you assume you are going to use the default [...]

Log File Sync and AWR – Not Good Bedfellows

Submitted by James Morle on Wed, 2010-06-02 12:32

I’m sure many of you are already enlightened enough about the dangers of ratios and averages, the most famous blunder of all being the ‘cache hit ratio’. It’s not that all ratios and averages are useless, but it is surely the case that most are useless, and that all can be misleading. This posting is [...]

Content thief

Submitted by Timur Akhmadeev on Wed, 2010-06-02 09:05

Do you happen to know Guenadi N Jilevski? If yes, then please tell him that stealing content is a bad idea. See: Select for update – unintended consequences – this is Mark Bobak’s Unintended Consequences Timing improvements in Oracle 11GR2 trace – this one is Alex Fatkulin’s Timing improvements in Oracle 11GR2 trace Oracle 11gR2 [...]

I wish .. (1)

Submitted by Jonathan Lewis on Tue, 2010-06-01 20:45

I pointed out some time ago a few of the things in SQL Server that I would like to see in Oracle. Here’s a couple more: Executions Plans Insert, update, and delete execution plans show the indexed access paths used to check the side effects of referential integrity constraints. (I haven’t  checked to see what [...]

Bitmap Index Degradation Since 10g (Fix You)

Submitted by Richard Foote on Tue, 2010-06-01 13:15

As discussed in my earlier post on Bitmap Index Degradation After DML Prior To 10g, Oracle wasn’t particularly efficient in the manner it maintained Bitmap Indexes after DML operations. During insert operations, if an existing Bitmap index entry didn’t cover the rowid range of a new row to be inserted, Oracle would create a new Bitmap index entry with a [...]

Listagg function in 11g release 2

Submitted by Adrian Billington on Tue, 2010-06-01 12:00

A new built-in function for string aggregation. June 2010

Skip Locked

Submitted by Jonathan Lewis on Mon, 2010-05-31 20:41

You may already be familiar with the syntax: select ... for update skip locked; It appeared (internally) some time back in Oracle 8i to implement some features of advanced queueing, but was only legalised and documented in one of the more recent versions of Oracle. If, like me, you checked the manuals to understand what [...]

DBMS_PARALLEL_EXECUTE

Submitted by Timur Akhmadeev on Mon, 2010-05-31 19:22

Here is a recent thread from OTN forums. The question raised is WTF? whether a hint in the examples section of DBMS_PARALLEL_EXECUTE documentation have to be used or not and why it is there. What do you think about it? Have a look in the documentation and mark your choice in a poll: PS. In [...]

Aanmelden AMIS Query: “An Evening with Doug Burns”

Submitted by marco on Mon, 2010-05-31 10:27

Doug BurnsOp donderdag 17 juni, vanaf 18:00 uur, zal Oracle Database Expert en Oracle ACE Director Doug Burns(Schotland), een kennisavond vullen met live demo’s op basis van de Oracle Enterprise Manager Diagnostic en Tuning Pack.

Deze bijzondere avond, geheel zonder slides, met de naam “How I Learned to Love Pictures – Oracle 10g/11g Performance Analysis Using OEM” zal alle in en outs van de Oracle Enterprise Manager Diagnostic en Tuning pack in geur en kleur, de valkuilen en de verstopte juweeltjes van de Oracle Enterprise Manager, demonstreren gebruik makend van onder andere Swingbench. Voor meer informatie, over Doug Burns of de inhoud van deze presentatie, zie de volgende blog posts en URL’s:

Wil je er bij zijn dan kun je je aanmelden voor deze AMIS Query, via de volgende URL:

8-)

Index Rebuilds

Submitted by Jonathan Lewis on Sun, 2010-05-30 20:57

A question came up on OTN a little while ago about an oddity during an online index rebuild. The original question describes how a relatively small index (500MB) takes several minutes to build, with a few minutes where users who are trying to update the table seem to be waiting for locks on the table [...]