Blog - comments

I read your blog.I like your blog.
machine vision lens

I read your blog. Thanks for sharing your blog.

Machine Vision Lenses
I have read so many articles or reviews on the topic of the blogger lovers but this piece of writing...
Sir,Good post, but I do not get the below statement for 12c:Moving a datafile online works in both A...
Gerard Alexander
Hi Morgan,thanks for both articles on Kerberos with Liferay, they were very useful to me! I use Life...
Blog Nicolas Jardot UKOUG 2012: Day 1 - Oracle 12c features and database performance

dbi services Blog

Welcome to the dbi services Blog! This IT blog focuses on database, middleware, and OS technologies such as Oracle, Microsoft SQL Server & SharePoint, EMC Documentum, MySQL, PostgreSQL, Sybase, Unix/Linux, etc. The dbi services blog represents the view of our consultants, not necessarily that of dbi services. Feel free to comment on our blog postings.

  • Home
    Home This is where you can find all the blog posts throughout the site.
  • Categories
    Categories Displays a list of categories from this blog.
  • Tags
    Tags Displays a list of tags that have been used in the blog.
  • Bloggers
    Bloggers Search for your favorite blogger from this site.
Posted by on in Technology Survey

UKOUG 2012: Day 1 - Oracle 12c features and database performance

Today was the official launch of UKOUG 2012. We started with keynotes including one from Tom Kytes giving information about Oracle 12c features.
Then I had some very interesting sessions on database performance. 

Oracle 12c 

When we talk about performance issues on SQL statement, it's really often due to bad/missing statistics and Oracle using the wrong execution plan. In next Oracle database two features may (or not) help us to deal with this topic:

  • Enhanced statistics
First, Oracle will automatically gather statistics on direct insert into an empty segment, when using a "create a select" statement for example there will be no need to gather statistics after the load.
Currently, the maximum number of buckets for a histogram is 254. So when the number of values is less than 254, Oracle gather a frequency histogram and store the count for each value. When the number is bigger, Oracle gather a height balanced histogram which is not efficient is there is a very popular value masking other enough important values. 
Enhanced statistics will introduce a new type of histogram to deal with that type of data distribution.
A new level for dynamic sampling will also be introduced, it will be automatic for parallel queries and persitent.
  • Adaptive execution plan
After the introduction of cardinality feedback in 11g, Oracle will introduce adaptive execution plans.
The database will be able to choose another plan in runtime of the cardinality does not correspond to the real number of rows fetched.
The optimizer will not require anymore running the statement once to see that the plan is bad and will adapt it in runtime.

The importance of being well connected

The session was presented by Graham Wood, a member of Real World Performance group.
With a few slides and a live demo he was able to convince me that with a smaller connection pool the database throughput is better.
In summary, with a big number of connections when the load increases the system might experience unstable performance due to contention in database and resource usage.
The throughput (number of transaction per second) can decrease when the load is too high.
Too many connections:
  • increase the contention in the database
  • increase the resource usage
  • increase the user response time
Reducing the number of connection to a smaller value:
  • increase the throughput
  • decrease the resource usage
  • reduce the user response time
Reducing the number of connection will force the middle tier to enqueue the queries but the database will work more efficiently than if there are many contention events.
See you in next days for more news from UKOUG 2012.
Rate this blog entry:

Nicolas Jardot has more than two years of experience in Oracle database management and Microsoft application development. He is specialized in Oracle tuning as well as in the Oracle Optimizer. Nicolas Jardot perfectly masters the behavior of the Oracle Optimizer, holding speeches on the topic at the Oracle OpenWorld 2013 and the UKOUG 2013. He is also specialized in C++ development and masters the programming of requests in SQL language. Nicolas Jardot has a solid experience in the virtualization and centralization of applications. He has developed several PL/SQL packages aimed to simplify the administration of database applications and maintains the DMK_SQL package of dbi services' Database Management Kit. Nicolas Jardot is Oracle Certified Professional 11g (OCP 11g) and ITIL Foundation V3 certified. He holds an Engineer's Degree in Computer Science from the University of Technology of Belfort-Montbéliard (F). His branch-related experience covers Pharma, Public Sector, Health, Real Estate, Automotive, etc.


  • No comments made yet. Be the first to submit a comment

Leave your comment

Guest Tuesday, 28 July 2015
AddThis Social Bookmark Button
Deutsch (DE-CH-AT)   French (Fr)


Contact us now!

Send us your request!

Our workshops

dbi FlexService SLA - ISO 20000 certified.

dbi FlexService SLA ISO 20000

Expert insight from insiders!

Fixed Price Services

dbi FlexService SLA - ISO 20000 certified.

dbi FlexService SLA ISO 20000

A safe investment: our IT services at fixed prices!

Your flexible SLA

dbi FlexService SLA - ISO 20000 certified.

dbi FlexService SLA ISO 20000

ISO 20000 certified & freely customizable!

dbi services Newsletter