Additional Journaling/Commitment Control Info From IBM

Group....  FYI if it helps anyone.  Larry is considered a premier source for 
HA, recovery, etc on the 400 

                                                                          


   1. What % of iSeries shops use journaling and commitment control?
   Answer: 35% of small shops,  85%-90% of large shops - - based on show of
      hands by audience when I give talks regarding database function to
      customers at the Rochester briefing center and at technical
      conferences and COMMON.  Penetration slightly higher in Europe than
      in the USA.

2.  People often avoid Journal/Commit for performance and space.  
   You're citing experience from 5 - 10 years ago.  There's been
      a sea change, especially since 9/11.  iSeries customers have been
      flocking to Rochester for advice regarding how to protect their
      businesses against the risk of disasters.   In addition, the recent
      security laws enacted in places like California have sent a flood of
      application providers our way seeking the audit trail benefits
      journaling provides.  Also the big swing in the past 8-10 years to
      round the clock use of web entry to their database has similarly
      convinced many that they need to do simple things like saving files
      while active and we consistency tell them that the only
      reliable/recoverable way to do so is to first enable journaling.  In
      addition, most large third-party vendors (SAP, JDE, PeopleSoft...)
      are shipping versions of their products which enable journaling by
      default - - so do any applications coded to use SQL on iSeries.   In
      addition, major new offering within the journal support within the
      past 3 years has made the overhead of journaling as well as the space
      consumed adjustable.  Using the proper tuning options, both the size
      consumed and the overhead incurred can be reduced in some cases a
      whopping 5 fold or more.  In addition, journaling now extends well
      beyond mere database protection and hence modern applications which
      seek to assure consistency among database files, data queues, data
      areas, and IFS stream files on iSeries are increasingly turning to
      journaling.  Net:  It's not your father's Oldsmobile.



3   On the other hand, measurement after measurement in our
      Rochester benchmark center has illustrated that the database caching
      which occurs when commitment control is employed (and is absent
      without commitment control) actually leads to regular conditions
      under which commitment control becomes a performance enhancer !!   -
      - Strange, but true !  Hence increasingly our business partners are
      modernizing their applications in order in incorporate commitment
      control.  In addition, once commitment control is present the related
      files and libraries become eligible for a new style of
      save-while-active introduced in V5R3.  Also, applications lacking
      commitment control can not receive the IBM seal of approval for being
      "Cluster-proven" which is required for some contracts.

4.  Use of commitment control assures that
      transaction consistency is assured by the operating system during the
      SLIC phase of IPL, long before any application approach gets a chance
      to view unrecovered transactions.  Commitment control is also an
      equal-opportunity player, assuring consistency within the same file
      across all users and all application packages which might elect to
      modify that file.  In addition, it simple performs better generally
      than raw database operations (due to the adaptive caching).

Larry Youngren/Rochester/IBM
  SLIC Journal-Commit Dev.