Thursday Jan 26, 2012

Fundamental Oracle flaw revealed??? Update ...!

Writing a blog has a nice effect on the side: it brings me in touch with people I've never met - but we have similar targets or interests. Today I've received a comment from Gökhan Atil about the Fundamental Oracle Flaw known also as the SCN issue.

And for sure I did visit Gökhan's blog and I did watch his very interesting 5 minutes demonstration how to bring down a database with the SCN issue. Which is very good to know as I thought the database won't come down because of this issue. But watch Gökhan's video by yourself and read his blog entry. And please note: this database was unpatched!

In conclusion we both come to the same recommendation:

Teşekkür ederim, Gökhan!

Thursday Jan 19, 2012

Fundamental Oracle flaw revealed??? Really ...?

This Infoworld article from Jan 17, 2012  Fundamental Oracle flaw revealed did alert Oracle database customers.Infoworld has raised this issue to Oracle before going public with it. Patches are included in the Jan 2012 CPU and PSU. So again, it's strongly recommended to apply the Jan 2012 PSU (or CPU if you are just asking for security fixes) to your environments.

What is the background of this issue?
Everything in an Oracle database is dependent on the SCN (System Change Number). This number is crucial to ensure read consistency. It will always be just incremented and is defined as a large 48-bit integer (281 trillion SCNs). But the SCN can jump as well - especially in cases of distributed transactions. Besides that hard limit there's also a soft limit for the SCN (see the MOS Note for more information).
Distributed Transaction

Hot backup bug
Now there's a backup bug which will increment the SCN to a much higher value once ALTER DATABASE BEGIN BACKUP gets used. We call this putting tablespaces into hot backup mode. Actually I'd assume that most people out there (at least those doing backups on a regular basis) use RMAN - and RMAN does not need to put anything into hot backup mode when creating online backups as the real downside of the hot backup mode is an increased value of log information.
Strong recommendation: Use RMAN! And you may apply patch 12371955: "High SCN growth rate from ALTER DATABASE BEGIN BACKUP in 11g" to your environment.

Combination of backup up and distributed transactions
The people who've detected this issue paint now a large Oracle database infrastructure to the wall - with many databases running distributed transactions - and a misbehaving BEGIN BACKUP routine in combination. This would elevate the SCN over and over again - on all interconnected databases - over time as the SCN will be synched over and over again - and will do huge jumps because of the backup bug.

What's the real risk?
I'm not a security expert - but I've seen many customer environments in the real world. I'd say (and skilled DBAs gotten interviewed by Infoworld and others stated similar opinions) it may be just a small risk in larger environments where many databases are connected together - and CPUs or PSUs got not applied on a regular basis. The PSU/CPU fix will prevent the SCN to be incremented in extensive jumps by several ways.
I'd completly disagree with Infoworld's prediction that databases will crash or abandon - transactions won't be executed anymore and an error will be raised. Yes, this is bad enough - true - but the database(s) will remain open.

What should you do?
Apply the January 2012 PSU or CPU and hot backup fix covered by patch 12371955. But keep in mind

  • Take the PSUs over CPUs as PSUs will contain also important non-dictionary changing fixes whereas CPUs contain security fixes only
  • You can't put a CPU on top of a previous applied PSU
  • Both CPUs and PSU are cummulative 
  • And well, you'll need Extended Support to get acces to PSUs or CPUs for Oracle Database 10.1 and 10.2 - and yes, please don't cry: We've asked you to upgrade a looooooong time ago ;-)

Monday Jan 09, 2012

Happy 2012 - and my music top tens ;-)

Dear All,

thanks for all your feedbacks, for visiting our workshops, for working together with us on upgrades and migrations, in reference projects, in escalated situations, thanks for all your respect and your support. We had a wonderful 2011 together with you and we all wish you a very Happy New Year 2012!!!

Thanks a lot!!!
Roy and Mike

P.S. As I never leave the house without my iPod or my iPhone and a pair of headphones here is my personal list of Top Ten Songs from 2011 - not only according to my listening stats iTunes is displaying ;-)

  1. Steve Wilson - Deform to form a Star
    Steve Wilson
    If you ever ... ever ... really ever in your life have the chance to watch Porcupine Tree (or Steve Wilson solo) live then grab this chance. I've seen so many concerts in the past but Porcupine Tree a while ago in Munich was one of the most impressive concerts I've ever been to. Their music is simply from somewhere outer space ...

  2. Anathema - Summernight Horizon
    Anathema got founded in 1990 in Liverpool as a Doom Metal band - but changed in the later 90s with their album Judgement to clear vocals and athmospheric sounds. I did listen to Judgement many many times (ask my good ol' Oracle support buddies - they will tell you ;-) ) in the past. But this year at OOW in San Francisco I passed by Rasputin Music near the cable car stop in Powell St. - and apparently had two Anathema albums in my hands. Summernight Horizon is just an example of the excellent We're Here Because We're Here album - mixed by (guess?) Steve Wilson from Porcupine Tree ;-) And yes, the album got released in 2010 but I did listen to it since October almost every second day.

  3. Bon Iver - Perth
    Bon Iver
    My album of 2011 - Bon Iver's self titled second album. Bon Iver is mainly Justin Vernon, a hermit from Wisconsin - and this CD is something you'll have to listen more than once. This music is full of open spaces - and I can't decode the meaning of all lyrics. But this isn't really important ...

  4. Bon Iver - Calgary
    --- see above ---

  5. Sólstafir- Fjara

    This band with the strange name (Sólstafir means Crepuscular Rays) is from Iceland. That's a really small island in the very very north-north-west of Europe with a small number of people, dramatic landscapes ... hey, and volcanoes ;-) Thanks Iceland (by the way!!). Anyway, this band got formed in 1995 and I have never heard anything about them until I've read a recommendation at my favourite news page They've played at Wacken Festival in 2010 - this is the largest Heavy Metal festival in the world in a small small town in northern Germany. And their 2011 album Svartir Sandar (meaning 'black sands') touched me from the first track to the end. Another great tune is Djákninn

  6. Mogwai - Death Rays

    I know Mogwai from Glasgow, Scotland, quite a long time. And their 2011 album Hardcore will never die, but you will (great title!) is simply outstanding. I did listen it for instance when walking through Stockholm in the night before my 2011 workshop. It's like a soundtrack for something which you see through your eyes with music tunes by Mogwai.

  7. It's all amazon's fault ;-) You know the recommendations "People who have bought this did buy as well ...". When I was listening to Bon Iver's self titled CD on their algorithms did recommend "Fink" to me. I've never heard of Fink before. And I simply did ignore it. But just a few days later a friend sent me an email asking 'Do you know Fink?' telling me about the great songs, lyrics and the wonderful voice of this guy. The same night I did order Sort of Revolution - and a few weeks later the 2011 album Perfect Darkness ...

  8. Girls - Vomit
    Sorry for this strange title (not my idea) but this is cool song, a cool video - and it was a recommendation of one of my favourite music pages in the web, They Shoot Music, Don't They from Vienna, Austria ;-)

  9. Feist - Caught a long Wind
    From Feist's 2011 album Metals recorded on a huge ranch at Big Sur in California. Great album, great song ...

  10. Coldplay - Paradise
    I own all Coldplay CDs. But their last one with the strange title Mylo Xyloto has been discussed very controversial in the web and the media. And I fully agree - it's somewhat a mediocre Coldplay album. And I've sold my copy right before christmas on ebay - but kept a copy on my iPod. I like to listen to Paradise and Charlie Brown but I've deleted other tracks such as the duet with Rhianna. I'd bet Chris Martin and his colleagues sell again millions - but if you'd compare this album to Parachutes or Rush of Blood ... ouch ... ;-)

    Happy 2012!!!


Mike Dietrich - Oracle Mike Dietrich
Master Product Manager - Database Upgrade & Migrations - Oracle

Based in Germany. Interlink between customers/partners and the Upgrade Development. Running workshops between Arctic and Antartica. Assisting customers in their reference projects onsite and remotely. Connect via:

- -


« January 2012 »
Slides Download Center
Visitors since 17-OCT-2011
White Paper and Docs
Viewlets and Videos
Workshop Map
x Oracle related Tech Blogs
This week on my Rega & Pono
Upgrade Reference Papers