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May 2014

Mysterious new Oracle compression type

As part of our research for our joint presentation at OGH.nl and E4 my colleague Frits Hoogland made an interesting discovery. He verified the compression format for updated rows previously compressed using Hybrid Columnar Compression (HCC). In that particular example we researched HCC data on Exadata storage. As you may know, reading HCC data in its compressed form is limited to Exadata, Pillar Axiom, and the ZFS Storage Appliance (ZFSSA).

Background

Enterprise Manager Customer Advisory Board, 2014

I’ve just returned from the Enterprise Manager Customer Advisory Board, aka EM CAB.  This is a special invitation-only program, provided by Oracle, that offers power users and top implementers of Oracle Enterprise Manager to come onsite and discuss the latest new features and enhancements to the product.  An NDA, (non-disclosure agreement) is required as part of the invitation due to the opportunity to revi

Compression Units – 6

I received an email recently asking me if I knew how Oracle found specific rows and columns in a compression unit. This is a topic that I’ve spoken about a couple of times, and I’ve published several notes on the blog about it, including an image of a critical slide from one of my presentations, and I was expecting to find some notes somewhere about Oracle catalogues all the bits and pieces.

Version control a multi-terrabyte database?! Yes !

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Can you version control database?

How do you manage databases in application development?  For all the advances in application development such as machine virtualization , agile development, devops practices, the database still stands as a huge barrier to development agility.

REPORT_UTL

So over last week off, I needed to write some reports to an old client of mine, and I remembered that at some point in the past I wrote a SVG plsql framework. So I decided to try and find it, and see what could be done with it. To my big surprise, I got a working report out the door, within a couple of hours, so it works and is ready to use.
It is very low level right now, but as an example of what you could do, try and see the following uptime report from an old client (names and other stuff redacted).

Sometimes it is just a coincidence!

Yesterday I was making a small config change to some test WebLogic domains. The change required a restart, so that’s what I did. The domains didn’t start up properly…

Being the last person to change the config, it was obviously something I had done that had broken them. I did the usual stuff of checking the log files and noticed some messages about not being able to write to a swap file. I did a “df -h” and noticed the mount point for the WebLogic installation was full. A quick bit of clean-up and everything started up fine.

So the moral of this story is one of the following:

  • Sometimes it is just a coincidence.
  • Don’t forget to configure your log rotation properly.
  • Never change anything in case it screws up and you get the blame.
  • “Just blame it on the guy who doesn’t speak English. Ahh, Tibor, how many times you’ve saved my butt.” ref

Cheers

What the heck are the /dev/shm/JOXSHM_EXT_x files on Linux?

There was an interesting question in Oracle-L about the JOXSHM_EXT_* files in /dev/shm directory on Linux. Basically something like this:

What the heck are the /dev/shm/JOXSHM_EXT_x files on Linux?

There was an interesting question in Oracle-L about the JOXSHM_EXT_* files in /dev/shm directory on Linux. Basically something like this:

What the heck are the /dev/shm/JOXSHM_EXT_x files on Linux?

There was an interesting question in Oracle-L about the JOXSHM_EXT_* files in /dev/shm directory on Linux. Basically something like this:

NFS max “rsize” on Solaris – gotcha

Laptop and Stethoscope

#555555;">When mounting NFS file systems there is an option to set the max rsize requested. For example:

#555555;">mount -o rsize=1048576,wsize=1048576,proto=tcp,vers=3  192.168.1.10:/foo /foo

#555555;">The general rsize used is 32K,  for example in Oracle documentation, but for large sequential I/O the larger rsize can make a big difference. In some tests the larger rsize was twice as fast.