Oracle database internals by Riyaj

Discussions about Oracle performance tuning, RAC, Oracle internal & E-business suite.

Video: deep review of LMS

Posted by Riyaj Shamsudeen on January 20, 2012

This video was created circa July 2011. Click the Read More link to review the video. Version Oracle Database

Synopsis: Essentially, we probe the importance of LMS processes using DTrace. Explain why LMS should run in elevated priority. How to review deep statistics about LMS processes and much more.

9 Responses to “Video: deep review of LMS”

  1. Hi Riyaj,
    excellent video presentation, but commands line are not much clear, could you share your slide presentation also ?
    Thanks a lot..

  2. Hi Riyai,

  3. Mike T said

    You need to increase the resolution on the video. The separate downloadable slides are nice, but the first 14 minutes of the presentation is basically unusable.

  4. Kitty said

    Terrific article! This is the type of information that should be shared
    around the net. Disgrace on Google for no longer positioning this submit higher!
    Come on over and talk over with my website . Thank you =)

  5. Rst Rst said

    Hi Riyas,

    I am a beginner on RAC..
    I am not getting about LMS from various blogspots … bit confused …please clarify !

    Snipet :
    If there is a consistent-read request, the LMS process rolls back the block , makes a Consistent-Read image of the block and then ship this block across the HSI (High Speed Interconnect) to the process requesting from a remote node.

    1) Consistent read request means —> A block is updated .. am i right ?
    2) Why LMS needs to rolls back the blcok ?

    Please clarify
    Thanks in advance.

    • Hi,

      Thanks for reading.

      SELECT statements have an SCN associated with them; for read consistency purposes, those statements can not see the changes beyond that SCN. So, when a process requests for a block, it is requesting a specific version of the block. If the servicing LMS process detects the block is ahead of the requested SCN, it tries to rollback the changes to create a block copy consistent with the supplied SCN. If the creation of the block with that SCN is successful, then LMS will send the block to the requester.

      Of course, there are numerous optimization, exceptions to discuss. Please read Expert Oracle RAC concepts chapter to understand further. I discussed these things in detail in that book.

      Hope that helps!

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