1 Reply Latest reply: Aug 26, 2009 6:00 PM by damorgan RSS

    Lob Compression

      Hi there,

      this question is to all of you who are using Advanced Compression for an adequate period in your productive systems.

      How does Lob Compression affect access performance?
      Does it always turns better / worse? ... My thoughts that it should be dependent on CPU power, right?
      Do you have recommendations regarding LOB caching?
      Which factors influence access performance?

      Who is familiar with the Lob Buffering Sub System? Can you provide me details on how to set up?
      This is a point I did not understand in the oracle docs...

      Thank in Advance Mathias
        • 1. Re: Lob Compression
          I have a lot of experience with Advanced Compression and, if you are attending OpenWorld, I will be presenting on 11gR2 A/C.

          Your assumptions are incorrect so lets start by correcting them.

          1. Inserts are inserts are inserts are inserts through Compression is irrelevant in every regard.

          2. Compression is partially dependent on CPU but also dependent upon your storage layer and the network connecting it to the server. In most cases CPUs can process far more data than storage subsystems are configured to deliver.

          What you have to do is look for what is preventing you from achieving infinite-speed processing. Are the disks incapable of delivering data faster? Is the network too slow, are there too few controller cards, too few HBA or NIC cards? Is it the bus? Is it the CPU? Then, and only then, can you determine whether adding CPU overhead will slow things down or ... by minimizing the number of bytes ... speed things up.

          3. LOB caching helps in some situations and is irrelevant or hurts in others. How many times will a cached LOB be used to answer other queries? Will using memory to store an LOB that is not reused help? I wouldn't expect so. To answer this question requires hands-on testing.

          4. All of them. I'm not being a arrogant here ... that is just the way it is. What affects it in one environment may be totally irrelevant in another.

          5. Open ended questions can not be answered. Many of us have experience with a lot of things. But our experience may not in any way relate to what you are doing. I suggest you go back to square one and figure out which version of Oracle and write some requirements based on an SLA.