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January 2013

dbms_xplan bug

Here’s a very long post (which is mainly an example) demonstrating a little bug in the “explain plan” functionality. It’s a variation of a bug which I thought had been fixed in 11g, but it still appears in some cases. Take a look at this execution plan, which comes from explaining “select * from dba_tab_cols” – the bit I want to emphasise is in lines 1 to 10:

Fedora 18 : Upgrading from Fedora 17…

I’ve just got to the end of a real upgrade of a Fedora 17 server to Fedora 18. The basic process goes like this.

  • Download the Fedora 18 ISO.
  • Update your current Fedora 17 system by issuing the “yum update” command and restart once it is complete.
  • Install the “fedup” package. “yum –enablerepo=updates-testing install fedup”
  • Run the fedup command pointing it to the Fedora 18 ISO you downloaded. “fedup-cli –iso /home/user/fedora-18.iso –debuglog=fedupdebug.log”
  • Check for errors in the log and correct if found.
  • Reboot the machine and select the “System Upgrade” option from the Grub menu.
  • Wait!

The system came up OK after this, but there are some gotchas. The first thing I did on completion was to run a “yum update” and lots of things were broken. Why? Well, after a lot of messing around and manually updating individual packages I finally figured out:

Fedora 18 and Oracle 11gR2…

After several abortive attempts I finally got hold of Fedora 18 last night. Those mirrors are getting a real battering at the moment. :)

The first job was to do a basic installation.

I’d seen a few things written about the new installer, not all of which were positive. IMHO the installation was a really nice experience. It is very different to previous installers, which probably freaks some people out, but I think it works really well.

What the heck is the INTERNAL_FUNCTION in execution plan predicate section?

Sometimes you see something like this in an execution plan:
-------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | -------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | | | 2 (100)| | |* 1 | TABLE ACCESS FULL| T | 1 | 22 | 2 (0)| 00:00:01 | -------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - filter("B"=INTERNAL_FUNCTION("A")) There’s quite a little information available about what the INTERNAL_FUNCTION really is and why does it show up, thus this blog entry.

What the heck is the INTERNAL_FUNCTION in execution plan predicate section?

Sometimes you see something like this in an execution plan:

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |       |       |     2 (100)|          |
|*  1 |  TABLE ACCESS FULL| T    |     1 |    22 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("B"=INTERNAL_FUNCTION("A"))

There’s quite a little information available about what the INTERNAL_FUNCTION really is and why does it show up, thus this blog entry.

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Oracle 11gR2 RAC Installation on Oracle Linux 5

As promised in a recent post, I’ve updated the Oracle 11gR2 RAC on Oracle Linux 5 article. It now uses VirtualBox 4.2.6, rather than 3.2.8 as it was before, and Oracle Linux 5.8.

I’ve purposely left it as an 11.2.0.1 installation as you can get this from OTN without needing access to My Oracle Support (MOS). The process works just as well for 11.2.0.3 and I would recommend you use that if you do have access to MOS. Remember, if you are doing the RAC installation on Oracle Linux 6 you are going to need 11.2.0.3, so OL5 might be the right option if you are playing around with this at home with no access to MOS.

Cheers

Tim…

Oracle Linux and ESX hot add cpu and memory

I'm still quite new in Vmware ESX environment and features which I'm using now as my lab (curiosity of VMWare Guru Program).
This time I decided to test hot add CPU and memory functionality. It looks very interesting and in past years hot cpu / memory games where restricted to sophisticated hardware only - now everybody can test is at home.

My lab is basesd on Intel 4 cores and VM are running Oracle Linux 6.3 with or without Oracle Enterprise Kernel. Here are my findings: