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Friday Philosophy – Memory (of the Human Kind) November 14, 2009

Posted by mwidlake in Perceptions, Uncategorized.
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One of the Joys of having been around for a while (I’ve hit that point where I occasionally find myself working with people who were not born when I got my first job in IT) is that you start to re-learn things. Well, I do. {I have to point out that, this being a Friday Philosophy, you will learn nothing yourself, especially not about Oracle. from this opost. If you want Oracle knowledge you might want to pop by Dion cho, Tanel Poder or Richard foote}

Several times over the last couple of weeks I have learnt something “new” and realised a little while later that I already knew it, but had forgotton (BLEVEL is one, consistent gets being impacted by array fetch size is another) . This is not something to be proud of – not knowing something you once did is far worse, and slightly worrying, then never having known it…

I like to think that it is all the new stuff I am learning, pushing previous knowledge out of my brain’s buffer cache {if it is not warmed by re-using it}, but I suspect that it might just be an uptime-related memory leak. A bit like having your database open for a few months and doing a lot of work that includes massive PL/SQL in-memory tables and hash joins (pickler fetches). No one seems sure of the exact mechanics, but after a while you have a hell of a lot less spare memory in your serever than you started with :-)

Maybe the memory loss is closer to the “pickler query” analogy than I thought, you can preserve soft tissue for a long time in alcohol. I’ll have another glass of wine and think on that.

This Forgetting Stuff was actually a major factor to my starting a blog. I was in the process of putting a load of notes on Oracle Odditites and things I had learnt from years past onto a web site so I could get at it from wherever I was in the world, and a friend told me I was being stupid – I should put them on a blog. So I did. There are only two little issues with this.

  • I can’t remember what I have already put on my blog.
  • I’ve forgotten where I put the ZIP disk with the notes on.

So I was contemplating this drift of knowledge and two things struck me.

1) I reckon that the very best people, in any area of expertise, are blessed with excellent memories. There is a comedian in the UK called Stephen Fry, and he is renowned for being stunningly clever. I think he probably is stunningly clever, but he also remembers everything he has learnt (Rory McGrath is another UK comedian with a perfect memory, but somehow he lacks the charm of Stephen Fry, and he has a beard, so not so highly renowned).
2) My poor memory is not maybe such a bad thing. I don’t have to get so upset when a whole chunk of my Oracle knowledge becomes obsolete. I used to be really good at sizing objects and utilizing space, taking into account the 5-block minimum, getting the extents to fit nicely into the datafiles, little scripts to resize segments into a small but sensibele number of extents to reduce wasted space, considering initrans, pctfree, pctused… Pretty much all pointless now :-)

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