3 Replies Latest reply: Dec 17, 2012 5:24 PM by Jimbo RSS

    OATM conversion - should I use unform or auto allocated extents

    Jimbo
      Hi, as part of an 11i to R12 E-Biz upgrade, I am migrating to the OATM model of tablespaces. One issue I am not sure about is whether to create the new OATM tablespaces so that they use Uniform Extents or whether I should set them to use Auto Allocate. I appreciate that some folk believe Auto Allocate can in the long run lead to freespace fragmentation. However I have not seen any recommendation from Oracle in any of the upgrade documentation as to which method of extent allocation to use.

      Q1. Any ideas on which is the recommended / better / wiser extent allocation method to use ?

      Q2. Are the concerns around free space fragmentation with the Auto Allocate method really likely ?

      Also when I ran the Sizing Report in the OATM migration utility against my existing non OATM 11i tablespaces to predict the space I required for the migration, I got very different results / predictions !

      For Uniform Extent Allocation I got the following prediction

      Required 20% buffer Current
      ======= ======= =====
      Total(in KB): 83,552,256 100,261,687 31,653,400

      For Auto Allocate I got the following prediction

      Required 20% buffer Current
      ======= ======= =====
      Total(in KB): 29,842,048 35,809,437 31,653,400


      Q3. Any idea why there is such a large variation between the predicted figures for both methods ?


      any insight or shared thoughts greatly appreciated,
      Jim