OT: Trip Report: Managing the Largest OLTP Database in the World

At the NoCOUG fall conference at the eBay town hall in San Jose, we got a first-hand look at the workings of the most complex database environments in the world.(read more)


I’m not very keen on bending the rules on production systems, I’d prefer to do things that look as if they could have happened in a completely legal fashion, but sometimes it’s necessary to abuse the system and here’s an example to demonstrate the point. I’ve got a simple SQL statement consisting of nothing more than an eight table join where the optimizer (on the various versions I’ve tested, including 12c) examines 5,040 join orders (even though _optimizer_max_permutations (more...)

Webinar Followup (Nov. 12) – In Search of Plan Stability – Part 2

Sorry for the delay in getting this posted, but thanks to everyone who attended my November 12th webinar entitled In Search of Plan Stability - Part 2. You can download the presentation materials from these links:

Presentation PDF


Great Lakes Oracle Conference 2015 call for speakers now open

Calling all geeks speakers big data nerds and application whiz kids the Great Lakes Oracle Conference ( GLOC ) is open for abstracts/presentation proposals ( May 18-20 2015 ).

This is a growing high quality regional conference in Cleveland where we are hoping to pass 350 ( 400? ) in attendance this year.  We have Kerry Osborne and Steven Feuerstein doing keynotes and on Monday 1/2 day workshops before the conference kicks into high (more...)

Oracle Database 12c : EXPAND_SQL_TEXT, APPROX_COUNT_DISTINCT, Session Sequences and Temporary Undo

While I was away on the OTN APAC tour, I wasn’t really able to sink my teeth into anything, so inspired by Connor McDonald‘s session in Perth, I decided to write up a few bits and pieces in my free moments in the hotels and planes (when I had enough elbow room to type).

Here is what I’ve neatened up so far.

OTN APAC 2014 : Summary

As you will have seen from my last post, I’m back in Birmingham after completing the OTN APAC 2014 tour. Here is a list of all the posts I wrote over the course of the tour.

OTN APAC 2014 : Auckland to Birmingham

Everything went smoothly at Auckland airport. Boarding an A380 takes quite a bit of time and I was near the front of the plane, so I was in the last group to board. Fortunately there was loads of room for hand luggage and the seat was pretty good. The people too my right were a couple, so they were leaning together, which gave me more elbow room. The extra room and a plug socket meant (more...)

Loading timestamp with timezone into a table using SQL Developer

I will start this post off stating  that I know there are better and more efficient methods of doing this but this is the best method I could come up with.

I had a csv file with a number of columns, one of which was data in a timestamp with timezone format.

A few rows looked like this – note I have stripped the other columns out for ease of display.

DeviceId    Timestamp
7941    11/9/2014 (more...)

VirtualBox 4.3.20

Just got home to find VirtualBox 4.3.20 has been released. I’ve just installed it on MaC (Yosemite), Fedora 20 and Windows 7 with no dramas so far.

The downloads and changelog are in the usual places.



VirtualBox 4.3.20 was first posted on November 22, 2014 at 4:11 pm.
©2012 "The ORACLE-BASE Blog". Use of this feed is for personal non-commercial use only. If you are not reading (more...)

New leafmisscount Option in Flex Cluster 12c

In the Oracle RAC previous version we have worked with the option “misscount” of crsctl, which applies for all the servers because there was only one kind of servers, but in the new version of Oracle (12c) we have a new kind of RAC configuration, the “Flex Cluster”. With Flex Cluster we have two kinds of servers “Hub nodes” and “Leaf Nodes”, the Hub Nodes have the same concept of the normal nodes in the previous versions, however (more...)

#DOAG2014 bits of info for DBAs

Just wanted to share some pieces of information from the recent DOAG annual conference that you may find interesting.

From Mike Dietrich’s presentation about Database Upgrade:

Mike Dietrich

Database Replay is extremely useful to predict after-upgrade performance on a test system,

especially we can record the production load on 10g even.

From Carsten Czarski’s talk about XML DB:

Carsten Czarski

With 12c, XML DB is mandatory and it provides an easy way to upload BLOBs via ftp into the (more...)

UKOUG and OU Team up at Annual Conference

The UK Oracle User Group (UKOUG) is hosting the Tech14 and Apps14 conferences jointly in Liverpool this year and I am proud to have been involved in organising the Oracle University Certification Exam  Test Fest.   User Group members attending the conference and who book in advance for one of the 120 available exam slots will get […]

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. I’ll explain why in a moment, but it made me think it might be worth setting up a very simple demonstration of the anomaly. I created a table t1 by copying view all_source – which happened to give me a table with about 100,000 rows and 1117 (more...)

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 (more...)

Dumb… no module named dom during startWeblogic.sh

ImportError: no module named dom This error suddenly appeared in two OAM environments, during startup of the stack, more specifically, weblogic startup (startWeblogic.sh). The complete stack is: $DOMAIN_HOME/startWebLogic.sh CLASSPATH=/oracle/middleware/patch_wls1036/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/oracle/middleware/jdk1.7.0_45/lib/tools.jar:/oracle/


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

  • No undo will be generated – in large direct path insert will free up large amount of data blocks
  • Less CBC latches (because of no UNDO blocks), less CPU usage
  • Readers need not undo the records, (more...)

OTN APAC 2014 : Auckland – Day 2

My day 2 at the conference started with my analytic functions session. I’m always a bit worried I oversimplify things, but people seem to appreciate it, so perhaps I’m just being paranoid. I’m sure the feedback will let me know. :)

Next I went to Chris Muir‘s session of Developing Web and Mobile Dashboards with Oracle ADF. I had already seen this at the AUSOUG WA event in Perth, but I liked it, so I (more...)

WordPress 4.0.1 Released

I got a bunch of emails this morning telling me by blogs had upgraded to WordPress 4.0.1. It’s a critical security release, so if you’ve not done an auto-update, you really need to get this sorted.

The downloads and changelog are in the usual places.



WordPress 4.0.1 Released was first posted on November 20, 2014 at 11:32 pm.
©2012 "The ORACLE-BASE Blog". Use of this feed is (more...)

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 (more...)

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,

If you have never helped organise a conference or user group meeting then you probably think there is (more...)