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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.

Parallel Costs

While creating a POC of a SQL rewrite recently I received a little surprise as I switched my query from serial execution to parallel execution and saw the optimizer’s estimated cost increase dramatically.

Why is “Dave Unknown” Trying to Social Media With Me?

I know some people share my opinion on this and others totally disagree – but I fail to appreciate why people I have never met, spoken with or care about want to Social Media with me. If we have not met but there is a high probability we share unusual interests then OK, perhaps – but the fact that we both can spell Oracle or know what a gene is does not count as unusual shared interests. Maybe I am just too old to “get it” or just too grumpy to appreciate their efforts.

Dumb... no module named dom during

ImportError: no module named dom
This error suddenly appeared in two OAM environments, during startup of the stack, more specifically, weblogic startup (
The complete stack is:



APPEND hint in oracle is very useful, there are many benefits
Fragmented data loading – data will clustered above the HWM so that similar data will be together. Otherwise Oracle will place the records in blocks using PCT_FREE rule

ODTUG from afar

I would like to extend my apologies to those people who persevered just now with our attempt to bring to you my presentation on APEX 5 Page Designer thanks to ODTUG.

Due to the massive time zone differences, the appropriate time on my end (6am) means I connect from home - where I'm limited to an ADSL connection. My location is even a bit of a dead zone for my smartphone's 4G plan which is normally better than my home internet speed. I considered just tethering the laptop to my phone, but I don't think it would have been an improvement.

Upgrading to – Dictionary View Performing Poor

Just a quick blog post on things you might see after upgrading to We recently upgraded database from to and query on some data dictionary views ran too slow.

1. Performace of query on dba_free_space degraded
2. Performance of query involving dba_segments is slow

DEV01> select ceil(sum(b.bytes)/1024/1024) b from sys.dba_free_space b;

Elapsed: 01:31:45.78

Searching MOS pointed to these Doc Ids :-

Conference Organisation from the Inside – UKOUG Tech14

An interesting experience I have had this year is being more involved in helping organise the annual UKOUG Oracle Technical Conference – Tech14 this year. I fully intended to blog about things as we progressed, but it never happened. But I thought it would be interesting to do a couple of blogs about it, for anyone interested,

Quantum Data

That’s data that isn’t there until you look for it, sort of, from the optimizer’s perspective.

Here’s some code to create a sample data set:

In-Memory Instance distribution with RAC databases: I want at least one instance that contains all the data

As you may know, with a RAC database, by default all objects populated into
In-memory will be distributed across all of the IM column stores in the cluster. It is also possible to have all the data appear in the IM column store on every node (Engineered Systems only). See this white paper for more details.

Progress update on my AWR repository

I received an email from a team member yesterday

Have you seen this?

Interesting idea – ever thought of implementing it?

Well of course I have implemented a AWR data repository and I thought I would catch-up on where I am with it and how it is being used.

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