2 Replies Latest reply on Jun 13, 2014 4:53 PM by Angelina84

    What affects the performance of SEM_NETWORK over time?

    Angelina84

      Et al,

       

      I have two oracle servers, old 11g and newer 12c.

      11g use to be fast but after about a year it got really slow: my queries would take 2+ times more than they use to.

      Loading SEM models took 2-3 times longer than in the past.

      Creating get_subject(triple) was nearly impossible.

      So, I asked my DBA to refresh SEM_NETWORK... After that 11g is running very fast.

       

      My new server, 12c, use to be very fast at the time when my 11g was very slow

       

      Now, 12c is awfully slow and what takes 5 minutes to run on 11g, it takes 2hours on 12c...

       

      We are setting up a new 12c server....

      Is this a trend... Is this something that will happen to all of my oracle dbs?

      If so, does anyone have any advice on how to handle this???

       

      I would be very grateful for any tip...

       

      Angelina

        • 1. Re: What affects the performance of SEM_NETWORK over time?
          Sdas-Oracle

          Angelina,

           

          From your description of the problem it seems that it may have to do with unused values not being purged from the values table in the semantic network. The proportion of unused values may become high if large semantic models containing blank nodes have been dropped since the creation of the semantic network.

           

          One way for a quick check for presence of relatively large proportion of blank nodes is to do a count of the various types of values in the values table:

          SELECT value_type, count(*) FROM mdsys.RDF_VALUE$ GROUP BY value_type;

           

          The following  semantics patch for 12.1.0.1.0 supports an operation for purging the unused values from the values table:

          Patch 18239544: SPATIAL AND GRAPH RDF SEMANTIC GRAPH 12.1.0.1.0 PATCH KIT (MARCH 2014)

           

          Please feel free to contact me directly at souripriya dot das at oracle dot com if needed.

           

          Thanks,

          - Souri.

          • 2. Re: What affects the performance of SEM_NETWORK over time?
            Angelina84

            There are not that many BN...

             

            SELECT value_type, count(*) FROM mdsys.RDF_VALUE$ GROUP BY value_type;

             

            VALUE_TYPE     COUNT(*)

            TL            27103534
            UR35404721
            PL8382163
            BN84