Top 60 Oracle Blogs

Recent comments

May 2013

BGOUG Spring 2013 : Day 1 (part 1)…

Last night we all got together to eat some food and chat. Julian Dontcheff is practically a savant where Bulgarian Poetry, World Cup match results and random Oracle facts are concerned. Although Christian Antognini was pretty impressive on the random Oracle facts too. :)

I didn’t have any presentations today, so I got to sit and watch. :) I’ve done loads of typing, mostly of syntax for 12c features, but it’s not really stuff that is worth posting, because I have no way to validate it out, so I’m just going to keep it as a reminder for when I get hold of 12c and can try it out.

The sessions I went to included:



The call for papers for UKOUG Tech 13 closed yesterday – though you may still be able to get something in if you visit the website before Monday. I’ve submitted a total of five – two of them aimed at novice DBAs and trouble-shooters – so I’ll probably get a couple of slots; and Tony Hasler has linked my name with a “round table”  (CBO – what else ?) and a “weird and whacky” which will be a reprise of the debate we had a couple of years ago about Oracle’s treatment of hints.

More importantly, for the immediate future, though – I’ll be speaking at the OUG Scotland conference which is only a few days away (12th June). It’s a one-day event with 6 concurrent streams of information covering DBA, Developer, APEX, BI, Apps and Cloud – so something for everyone.

“alter session force parallel query”, and indexes

This post is a brief discussion about the advantages of activating parallelism by altering the session environment instead of using the alternative ways (hints, DDL). The latter ways are the most popular in my experience, but I have noticed that their popularity is actually due, quite frequently, more to imperfect understanding rather than informed decision - and that's a pity since "alter session force parallel query" can really save everyone a lot of tedious work and improve maintainability a great deal.

We will also check that issuing

alter session force parallel query parallel N;

is the same as specifying the hints

/*+ parallel (t,N)  */
/*+ parallel_index (t, t_idx, N) */

for all tables referenced in the query, and for all indexes defined on them (the former is quite obvious, the latter not that much).

Linux large pages and non-uniform memory distribution

In my last post about large pages in I promised a little more background information on how large pages and NUMA are related.

Background and some history about processor architecture

Extreme Exadata Expo Speakers Announced

Thanks to everyone that submitted abstracts for our upcoming E4 conference. Unfortunately, there were more quality submissions than we had room for. Maybe next year we should expand the event to 3 days. :) But in the meantime, we have assembled what I believe is an excellent line up of speakers. I’ll just mention a few highlights here:

Tom Kyte will be doing the keynote. Enough said!

Maria Colgan and Roger MacNicol will be doing a 3 hour combined session on smart scans. Maria will attack the topic from the top down (optimizer) point of view (since she is the product manager for the optimizer) and Roger will be attacking it from the bottom up (since he is the lead developer for the smart scan code). This should be an awesome session and Tanel Poder has already said he was going to line up the night before.

BGOUG Spring 2013 : Day -1

It’s stupid o’clock in the morning and I’m waiting for my taxi to arrive. Considering how close Bulgaria is, it takes me a very long time to get there.

I am a mix of excited and nervous. This is my first conference this year, so all the usual insecurities are in full effect, from fear of flying to the constant nagging thoughts that perhaps I don’t know anything about Oracle and maybe I shouldn’t be on stage acting like I do. :)

I’m sure it will go OK and it will be nice to meet up with the gang again.



Follow-up: Using Optimizer Hints for Oracle Performance Tuning Webinar

Thanks to everyone who attended my webinar on using hints for Oracle testing and performance tuning. As usual, it was a great event and I appreciate the comments and questions.

Presentation PDF
Related scripts
Webinar recording

I'll be back in the saddle again in July so keep your eyes open for the announcement of that event. Thanks again and hope to see you then!

Datatype discipline

(This is based on some ‘issues’ a client was having, so the example is architected to make a particular point, but is relevant nonetheless)

In the distributed database world, we often have different names for the same piece of information.

Consider two tables which hold customer information.  In one table, they called the customer key "REF_NUM", and in the other table "CUST_ID".

That’s not ideal, but it’s not a big drama because at least the data types align.

Clustering Factor Calculation Improvement Part II (Blocks On Blocks)

My previous post on the new TABLE_CACHED_BLOCKS statistics gathering preference certainly generated some interest My blog hits for the week have gone off the charts !! One of the concerns raised by this new capability was that setting such a preference might result in really unrealistic and inaccurate Clustering Factor (CF) values, especially for those […]

More on use_large_pages in Linux and

Large Pages in Linux are a really interesting topic for me as I really like Linux and trying to understand how it works. Large pages can be very beneficial for systems with large SGAs and even more so for those with large SGA and lots of user sessions connected.

I have previously written about the benefits and usage of large pages in Linux here:

So now as you may know there is a change to the init.ora parameter “use_large_pages” in The parameter can take these values: