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June 2009

on the importance of being agile

If you're expecting something in favor Agile development, you're on the wrong blog. You'll notice that my 'agile' uses a little 'a' - I'm referring to the adjective agile, defined on as: 1. Characterized by quickness, lightness, and ease of movement; nimble. 2. Mentally quick or alert: an agile mind.or in the Merriam-Webster dictionary: 1 : marked by ready ability to move with

Oracle Interface for Google Visualization API (external data source interface)

I have been looking for a while at the Google Visualization API and finally found a way to produce the required JSON to produce any graphs directly and indirectly from Oracle database. I will make a white paper available on how to do this. Checkout this link: The procedure handles the SQL that the Google API uses (not for all functionality yet (pivot, offset, format are not yet supported).

More on this later.

The Helsinki Platform

Nice picture from "OraDude" showing the Fat Database, or Helsinki's first observation.

Dynamic sampling and partitioned tables


Update January 2010: A thread on OTN mentioned this blog post and another, actually contradicting blog post by Asif Momen.

So why are these two blog posts coming to different conclusions regarding Dynamic Sampling and partitions with missing statistics?

This is the good thing with documented test cases - I reproduced what Asif has done and found out that the significant difference between these two test cases is the existence of global level statistics.

In my test case below, I have explicitly gathered statistics only on partition level, and there are no statistics on global level/table (which can be seen from the output of the query against user_tab_statistics below).

Asif has actually gathered statistics on global/table level which can be seen from his blog post.

So the conclusion seems to be: If you prune to a single partition, but this partition has no statistics, then Dynamic sampling will be used if no global/table level statistics are available. If global/table level statistics are available, the optimizer won't perform dynamic sampling and revert to these global/table level statistics instead.

Oddly this obviously doesn't apply to the subpartition/partition level case: Repeating a similar setup with subpartitions having no statistics, but statistics on partition level are available, Dynamic Sampling still was used (tested on Win32).


Diagnosing and Resolving “gc block lost”

Last week, one of our clients had a sudden slow down on all of their applications which is running on two node RAC environment

Below is the summary of the setup:
– Server and Storage: SunFire X4200 with LUNs on EMC CX300
– OS: RHEL 4.3 ES
– Oracle (database and clusterware)
– Database Files, Flash Recovery Area, OCR, and Voting disk are located on OCFS2 filesystems
– Application: Forms and Reports (6i and also lower)

As per the DBA, the workload on the database was normal and there were no changes on the RAC nodes and on the applications. Hmm, I can’t really tell because I haven’t really looked into their workload so I don’t have past data to compare.

Two weeks to go for ODTUG

ODTUG Kaleidoscoop 2009 is approaching soon. I'll be hosting two presentations.Fat Databases: a Layered ApproachThis will basically be the Helsinki Declaration talk, only crammed into just one hour. I'll probably skip the four observations and go straight to the WoD application and its code classification (DL, BL and UI-code). And close with a short demo by building a page (with Apex of course)

Rebound for database design?

My fellow Oaktable member Robyn Sands posted something very "inline" with the Helsinki declaration. Good comments too.