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  • Adventures in RAC: gc buffer busy acquire and release

    It seems that I’m getting more and more drawn into the world of performance analysis, and since I sometimes tend to forget things I need to write them down. I almost enjoy the “getting there” more than ultimately solving the problem. You pick up quite a few things on the way. This environment is Exadata…

  • UKOUG post conference geek update part 1 – ACFS for Oracle databases

    One of the many interesting things I heard at the conference this time around was that Oracle’s future direction includes the use of database files on ACFS. When ACFS came out this was strictly ruled out, but has been possible for a little while now, I believe with 12.1.0.1.0. With the Oracle Database Appliance (ODA)…

  • Little things worth knowing: creating the Swingbench order entry schema “lights out”

    This is a little note, primarily to myself I guess, about the creation of the order entry schema (part of Swingbench, written by Dominic Giles) when no VNC sessions are available. Instead, you can create the schema on the command line. I always execute commands on remote systems in a screen session for increased peace of…

  • Concurrent statistics gathering in 12.1.0.2

    Prompted by an actual task at hand I spent some time investigating an 11.2.0.2 feature – concurrent statistics gathering. It has been on my to-do list for quite some time but so far I didn’t have a use case, and use cases make it so much easier. The question was-how can I gather statistics on a…

  • Little things worth knowing: ORACLE_SID, instance_name and the database names in Clusterware

    If you ever wanted to know how Clusterware works with registered database resources, read on! It takes a little while to get your head around the concepts of the ORACLE_SID, the instance_name and the database name as well. And how Clusterware deals with all of them. Although this post has been written on 12.1.0.2.0 on…

  • Interesting observations executing SLOB2 with ext4 and xfs on SSD

    My lab server has 2 SSDs, one is connected using SATA 2 and another is connected using SATA 3. I’d expect the SATA 3 connected device to be equally well equipped or even better to do work than the “old” interface. I ran SLOB on these devices to find out if there was a difference.…

  • Exadata and Virtual Private Database: will it offload my query?

    During one of the classes I taught about Exadata optimisations I had an interesting question: If I am using VPD, will Exadata still offload the query? Background is that we discussed function offloading, and the meta-view v$sqlfn_metadata. It turned out that SYS_CONTEXT() is not offloadable in 11.2.0.4. Since I’m a great fan of the Tom…

  • Little things worth knowing-troubleshooting parallel statement queueing

    This is yet another one of these posts that hopefully help you as much as they are going to help me in the future. Recently I enjoyed troubleshooting a problem related to parallel execution. Since I have never really written down how to tackle such a problem I thought it might be nice to do…

  • Interesting observation about standby redo logs in Data Guard

    Some of you might have followed the discussion around the number of standby redo logs on twitter, but since 140 characters are woefully short for the complete story here’s the writeup that prompted the question. This is a test with 12.1.0.2 on virtualised Linux, repeated on a proper platform with physical hardware. UPDATE: This is…

  • Can you have high redundancy files in a normal redundancy diskgroup?

    One of the perks of teaching classes is that I get to research questions asked. In the last Exadata Administration Class I taught someone asked: can you have your disk groups in Exadata on normal redundancy yet have certain databases use high redundancy? This would be a good interview question … The answer is yes,…