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  • How to get insights into the Linux Kernel

    This is probably as much a note-to-self as it can possibly be. Recently I have enjoyed some more in-depth research about how the Linux kernel works. To that extent I started fairly low-level. Theoretically speaking, you need to understand the hardware-software interface first before you can understand the upper levels. But in practice you get…

  • Upgrading clustered Grid Infrastructure to 12.1.0.2 from 12.1.0.1.3

    Oracle 12.1.0.2 is out, after lots of announcements the product has finally been released. I had just extended my 12.1.0.1.3 cluster to 3 nodes and was about to apply the July PSU when I saw the news. So why not try and upgrade to the brand new thing? What struck me at first was the…

  • Implications of threaded_execution = true in 12c

    I had an interesting discussion as part of my latest presentation at the UKOUG RAC CIA & Database Combined SIG. Part of my talk was about the implications of the new threaded execution model in Oracle. Since “we do not use Windows” (except for gaming) I can’t compare the Windows thread model to the new…

  • Setting up Direct NFS on Oracle 12c

    Direct NFS is a great feature that I have finally had the time to investigate further. Since I always forget how to set it up and I didn’t find blog posts about this subject elsewhere I decided to put something together. In this configuration I am using a virtual machine named server1 to export a…

  • Why is P1 the only parameter populated in cell smart table scan?

    Anyone who has looked at Exadata might ask the question, and I did so too. After all, cell smart table scan is in wait class User IO so there should be more, right? This is what you find for a smart scan: Compare this to the traditional IO request: At first I didn’t understand as to why…

  • Why does the Optimiser not respect my qb_name() hint?

    I recently was involved in an investigation on a slow-running report on an Exadata system. This was rather interesting, the raw text file with the query was 33kb in size, and SQL Developer formatted the query to > 1000 lines. There were lots of interesting constructs in the query and the optimiser did its best…

  • My SDU goes to 11 ^h^h I meant 2097152

    One of the cool new things in 12.1 is that you can set the Session Data Unit to 2MB. This might not sound like a Big Deal, but getting this to work required me to dig deeper into the TNS layer than I intended…Then I somehow got stuck on the wrong track, thankfully the team…

  • RAC 12c enhancements: adding an additional SCAN-part 4

    This is going to be the last part of this series, however long it might end up being in the end. In the previous articles you read how to create a physical standby database from a RAC One database. Networks (refresher) To make it easier to follow without going back to the previous articles, here…

  • 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…

  • RAC 12c enhancements: adding an additional SCAN-part 3

    Travel time can be writing time and while sitting in the departure lounge waiting for my flight I use the opportunity to add part 3 of the series. In the previous two parts you could read how to add a second SCAN and the necessary infrastructure to the cluster. Now it is time to create…