Martins Blog

Powered by
WordPress

  • Little things worth knowing: Is there a penalty in establishing a connection to Oracle using the MAA connection string? Part 2

    In the very lengthy previous post about the MAA connect string I wanted to explain the use of the MAA connection string as promoted by Oracle. I deliberately kept the first part simple: both primary and standby cluster were up, and although the database was operating in the primary role on what I called standby…

  • Little things worth knowing: Is there a penalty in establishing a connection to Oracle using the MAA connection string?

    Sorry for the long title! I had a question during my session about “advanced RAC programming features” during the last Paris Oracle Meetup about the MAA connection string. I showed an example taken from the Appication Continuity White Paper (http://www.oracle.com/technetwork/database/options/clustering/application-continuity-wp-12c-1966213.pdf). Someone from the audience asked me if I had experienced any problems with it, such…

  • Little things worth knowing: what does opatchauto actually do?

    I recently applied system patch 20132450 to my 12.1.0.2.0 installation on a 2 node RAC system on Oracle Linux 7.1. While ensuring that OPatch is the latest version available I came across an interesting command line option in opatchauto. It is called “-generateSteps”. So this could be quite interesting so I wanted to see what…

  • Little things worth knowing: direct path inserts and referential integrity

    This is another post to remind myself that Oracle evolves, and what I thought I knew might no longer be relevant. So double-checking instead of assuming should become a habit! Today’s example: direct path inserts. I seemed to remember from Oracle 9i that a direct path insert ignores referential integrity. This is still confirmed in the 9i…

  • Little things worth knowing: exp/imp vs expdp and impdp for HCC in Exadata

    Do you know the difference between exp/imp and expdp/impdp when it comes to importing HCC compressed data in Exadata? If not, then follow me through two examples. This is on 11.2.0.3/11.2.3.3.1 but applies to all database releases you can have on Exadata. The task at hand is to export a table (which happens to be non-partitioned…

  • Understanding enhancements to block cleanouts in Exadata part 2

    In part 1 of the series I tried to explain (probably a bit too verbose when it came to session statistics) what the effect is of delayed block cleanout and buffered I/O. In the final example the “dirty” blocks on disk have been cleaned out in the buffer cache, greatly reducing the amount of work…

  • Understanding enhancements to block cleanouts in Exadata part 1

    Travel time is writing time and I have the perfect setting for a techie post. Actually I got quite excited about the subject causing the article to get a bit longer than initially anticipated. In this part you can read about block cleanouts when using buffered I/O. The next part will show how this works…

  • What happens in ASM if usable_file_mb is negative and you lose a failgroup

    Having read the excellent post “Demystifying ASM REQUIRED_MIRROR_FREE_MB and USABLE_FILE_MB” again by Harald von Breederode I wanted to see what happens if you create a setup where your usable_file_mb is negative and you actually have to rebalance after a fatal failgroup error. I am using 12.1.0.2.0 on Oracle Linux 6.6/UEK3 in a KVM in case anyone…

  • How to resolve the text behind v$views?

    This is a common problem I have and I never write it down (except now). For example, today I wanted to know what the valid parameters for _serial_direct_read were: OK so if Oracle doesn’t tell me then maybe I can work it out? Getting the view_text has worked in the past: I’m sure I did…

  • Adaptive plans and v$sql_plan and related views

    Adaptive plans are one of the coolest new optimiser features in Oracle 12c. If you haven’t seen or heard about them in detail I recommend the following resources: Kerry Osborne’s presentation about the feature (and a link to the recording) Tim Hall’s article about the same feature Link to adaptive plans in the official documentation…