Thursday, April 28, 2005

Things you know

do you prioritize what "new things" you'll be learning first?

From a presentation I give about 'things you know'... I have this list

(you will have to read this list more than once to "get it", they are tongue twisters all, read them one word at a time deliberately, that helps me)

1) Things you know you know (you've used them, you've proven them)

2) Things you know that you don't know you know yet (you have the bits and pieces, just haven't put them all together)

3) Things you don't know that you know you don't know. (things you haven't used yet in real life)

4) Things you don't know that you don't know you don't know (follow on from #3, if you haven't used something, there is so much about it you don't even know you don't know yet)

5) Things you know that just ain't so

These are what I look for, categorize things into.

#2 is something I look for, like an unexplained phenomena in the database, just figured one out yesterday with read consistency and 10g. My scripts had all changed in their behavior between 9i and 10g -- the ones I've been using for a long time. I could not explain it. Yesterday, all of a sudden, in a flash of intuition, I could - and proved it (as in provided myself compelling evidence that what I thought was true was in fact the cause). It was dynamic sampling kicking in and changing the number of IO's a query would do... I had a script that in 9i and before would consistently show that after 10,000 updates of a row (followed by commit), a query opened before the updates would do 10,000 IO's to rollback the changes. In 10g, sometimes it was 3 IO's, sometimes 500, sometimes thousands - but never 10,000. Made me really nervous presenting - because I knew it would show something - but not sure what I would see. Now I know why (and I knew why, I just never put the pieces together) Dynamic sampling would query the table and sample the blocks - and do some of the rolling back I needed to have done and I would take advantage of it. Analyze the table up front and I'm back to 10,000 IO's every time. I didn't know I knew why, hadn't tied all of the bits and pieces together.

#3 is really easy. Those are the technologies I have on a list of "things to learn about". I really need to do a deep dive into ASM, but I need the project to drive it. I learn things like that by doing them for real a couple of times. Just playing with it in a lab doesn't always get me where I need to be. It might not be something I get to for a while, but it is on my list. But I do need a real project to work with it on. (streams is high on the list too but the same caveat applies, I'll need a project to learn it right).

#4 is one I don't have too much of a problem with. Anything I haven't actually used in real life. I tend not to talk about them too much. I don't know what I don't know about them so I avoid pretending I do. It is an extension of #3 in that unless and until you've used something a lot, there is a ton about it you don't even know you don't know yet. I try to learn about them as I go along, but try not to talk too much about it until I do.

#5, that is a recurring theme for me. Question Authority. Show me. Prove it (as in show me compelling evidence that you know what you say is true). Don't ask me to "trust you", because I don't trust me, why should I trust you. We are all full of #5, our backgrounds and experiences guarantee that. This paper I wrote is all about #5. We all know things that just ain't so.

Today for example, going through Expert One on One for the second edition. I am fairly impressed by what I did in 2000/2001 (although sometimes I also find myself saying "doh, did I really say THAT"). Not the book itself but rather the way the book speaks for itself. I had never written one before that but it is holding up rather well. When it is wrong about how something works in 9i/10g (because it was written for 8i and before), it tells me! It didn't know it would be wrong, but it tells me. How? The test cases. They all run, but some with different results. So the funny thing is I'm discovering new things about 10g that I didn't know before - and 10g is different in many ways from 9i I'm finding. And 9i from 8i. Just by replaying the book. Little things, big things. Little thing - test case on how triggers affect redo generation of inserts, updates, deletes. Ran it in 10g and said "wow, 8i did it differently". Ran it in 9i and said instead "wow 10g is unique". The rules changed. Many of them have. Silent array fetching in PLSQL, redo generation different, memory allocation - way way different. Big things -- even subtle differences in 10g over 9i - anyone notice that in 10g shared_pool_size the parameter equals the sum(bytes) from v$sgastat - that'll never happen in 9i and before. What does it mean to you? Well, that your shared pool is smaller than you think it is in 10g if you didn't increase the shared_pool_size when you upgraded. All of the little bits that added onto it in 9i and before, STEAL from it in 10g. For example, my shared_pool_size of 80m in 9i resulted in a 96m shared pool. In 10g, it would be rounded up to the granule size (probably 80 meg actually since that is divisible by 4, 8 and 16. Ok, so I cannot write "probably", it will be 80 meg on RHAS 3.0 32bit Oracle 10g) and would be 16 meg SMALLER than in 9i.

So, I don't really prioritize what I learn, they just keep sort of hitting me in the face from time to time. Slap slap, wake up, something new is here. And it is always nice to know. I just file it away for when I need it.
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26 Comments:

Anonymous Matthias Rogel said....

intuition

great to read this word.

very underestimated in my opinion.

in all these discussions during the last
weeks concerning scientists I really
missed that word.

I think a good scientist has a good intuition.
You as mathematician know S. Ramanujan, he is the best example.

of course proof is needed but how to
find out what you want to prove ?

intuition is the keyword.

(might be off-topic but just came into my head when reading this article)

Thu Apr 28, 07:16:00 AM EDT  

Anonymous Anonymous said....

Looks like you are quoting the Donald Rumsfield doctrine of known-unknown matrix !!!

Thu Apr 28, 07:47:00 AM EDT  

Blogger David Aldridge said....

>> anyone notice that in 10g shared_pool_size the parameter equals the sum(bytes) from v$sgastat - that'll never happen in 9i and before. What does it mean to you? Well, that your shared pool is smaller than you think it is in 10g if you didn't increase the shared_pool_size when you upgraded. <<

Oooh, I did notice that! Well I noticed that I couldn't reproduce an "issue" that someone reported -- I guess that they were on 9i. I did think "Wow, that's pretty buggy, that view".

So I guess I have to move that bit of knowledge from one category to another now.

Thu Apr 28, 09:17:00 AM EDT  

Anonymous Anonymous said....

You're just trying to give us a headache right? %-)

Martin

Thu Apr 28, 09:49:00 AM EDT  

Blogger Alberto Dell'Era said....

lot of experience => strong intuition

Thu Apr 28, 09:52:00 AM EDT  

Anonymous Shawn Brockway said....

After reading your latest blog entry, I couldn't help but think about a strange look I received from an interviewer. The manager asked me what I felt was the most important thing I had learned about Oracle in 4 years as a DBA. I promptly replied that the more I learn about Oracle, the more I realize I how little I know about Oracle. Somehow, I don't think that was exactly the answer that he was expecting. I did go on to explain that for every concept that I come to understand, two more concepts are brought to my attention that I never realized existed.

Thu Apr 28, 11:42:00 AM EDT  

Blogger DaPi said....

This comment has been removed by a blog administrator.

Thu Apr 28, 02:40:00 PM EDT  

Blogger DaPi said....

Eastern (presumambly old) version of the know/don't-know matrix:

If he knows not, and knows not that he knows not, shun him.
If he knows not, and knows that he knows not, teach him.
If he knows, and knows not that he knows, wake him.
If he knows, and knows that he knows, follow him.

Thu Apr 28, 02:42:00 PM EDT  

Blogger DaPi said....

"I promptly replied that the more I learn about Oracle, the more I realize I how little I know about Oracle"

Shawn's in good company:
"As our circle of knowledge expands, so does the circumference of darkness surrounding it." --Albert Einstein

Thu Apr 28, 02:47:00 PM EDT  

Blogger David Aldridge said....

DaPi, I can't believe that you didn't point out that the knowledge:darkness ratio is therefore proportional to 1:1^0.5

Thu Apr 28, 02:52:00 PM EDT  

Blogger DaPi said....

David (slim), Einstein would have thrown up his hands in horror! Everyone knows that it will depend on the local value of:
R(ab) - 1/2R.g(ab) [writing (ab) for the subscripts]

Thu Apr 28, 03:28:00 PM EDT  

Blogger Thomas Kyte said....

DaPi -- I like the eastern version but....

...If he knows, and knows that he knows, follow him....

what if he only thinks he knows, how do you know that he doesn't know what he is sure he knows?

as for the other stuff -- geek alert. We all know ratio based knowledge is....

Thu Apr 28, 03:47:00 PM EDT  

Blogger DaPi said....

"what if he only thinks he knows, how do you know that he doesn't know what he is sure he knows?"

I DON'T KNOW :)

Thu Apr 28, 05:19:00 PM EDT  

Blogger Connor McDonald said....

"As our circle of knowledge expands, so does the circumference of darkness surrounding it."

I prefer to tell to it our DBA's like this...

"You longer you stay at *just* your current knowledge, the less and less you end up knowing"

You gotta keep movin...

Thu Apr 28, 08:27:00 PM EDT  

Anonymous Anonymous said....

To Connor,
When will the empty blog start filling up?

Thu Apr 28, 08:49:00 PM EDT  

Blogger Kevin said....

Tom -- a couple of days ago, you wrote about Odyssey of the Mind. Which project did your son do? (I was a judge at the Loudoun competition).

You have my admiration for being able to go back and read your past work. I reread some of my college papers a couple of years ago, and the only thing I could say afterward was 'Gaaak'.

Thu Apr 28, 09:38:00 PM EDT  

Anonymous Doug C said....

Tom - I currently don't have a question for asktom. I think some of Woody Lons that influenced you has influenced me from your site. - couple degrees of separation. I generally run my own experiments and don't ask as many questions as I used to. That being said I am sure I'll have a few below-par questions eventually. :-) However, I couldn't help but notice that "In the last 4 weeks, I've taken X questions".. has been steadily declining for.. oh.. about 4 weeks. In fact it's down to 2 as I write this. Just curious, are you trying to make a point.. or are you just too darn busy with this blog - or...

Thu Apr 28, 10:11:00 PM EDT  

Blogger David Aldridge said....

>> I really need to do a deep dive into ASM, but I need the project to drive it. I learn things like that by doing them for real a couple of times. Just playing with it in a lab doesn't always get me where I need to be. <<

Exactly! That's a relief -- I was thinking it was a character flaw, or that I had the attention span of a gnat because I can't learn stuff that i have no practical use for right now. Glad someone else is the same way.

I've been meaning to learn Italian ever since marrying a native, but unless we know that we're going to move there for a few years *fingers-crossed* it just ain't going to happen.

I know little about RMAN, and much less than I feel I ought to about backup and recovery in general, because it has never been my job to do that stuff. Books, white papers, none of it makes any impression on me until I have to do it for real.

Thanks Tom!

Thu Apr 28, 11:13:00 PM EDT  

Blogger Thomas Kyte said....

I currently don't have a question for asktom.

For the month of april, I decided to take no new questions while working on the book.

It'll be back in business in May.

Fri Apr 29, 07:18:00 AM EDT  

Anonymous Anonymous said....

"I know little about RMAN ... none of it makes any impression on me until I have to do it for real."

Believe me, you don't want to learn RMAN when you have to use it.

Fri Apr 29, 09:15:00 AM EDT  

Blogger Thomas Kyte said....

a couple of days ago, you wrote about Odyssey of the Mind.

They were a division II "Stunt Mobils" team.

Their job (remember they are 12/13 years old):

build two vehicles from scratch (no kits).

They must be self powered, and self guided, no remote controls or anything like that.

They had to go over 5 courses. with different obstacles (meaning they needed some sort of guidance system).

They had $140 max to spend (and they had to get the money themselves).

And a big list of rules to follow -- and they were responsible for it all. We facilitated. A big "no outside asssistance" rule. It was really hard not to dive in and do it. They had to build some prototypes and test things out.

It was cool -- I'll probably do it again.

Fri Apr 29, 10:01:00 AM EDT  

Anonymous Anonymous said....

I suggest you to read the following book:
http://www.amazon.com/exec/obidos/tg/detail/-/9810202679/qid=1114803879/sr=8-3/ref=sr_8_xs_ap_i3_xgl14/103-9525039-1071064?v=glance&s=books&n=507846

Fri Apr 29, 03:58:00 PM EDT  

Blogger Kevin said....

One of the teams from our school (Aldie) did that project. That was one of the toughest I've seen, and I've been doing it for five years.
It's so much fun watching the kids, and I've always seen something extraordinary.

Sat Apr 30, 09:50:00 AM EDT  

Blogger Slava said....

Tom,

thank you, it is quite an answer, I hope it didn't distract you too much from R2 of your book :)

Sat Apr 30, 11:22:00 PM EDT  

Anonymous Anonymous said....

Interesting, the whole You Know You Know concept.....

Attended a presentation by a U of MN prof. at a local Chamber of Commerce meeting back in 92....

You Know You Know
You Know You Don't Know
You Don't know You Don't Know

Everything else fits into one of the 3 main categories.

Wish I could remember her name. Seems like this is a philosophy that’s been around for a long time.

I like most of the sub-categories listed here, though some appear to be fluffy.

Tue Oct 18, 12:14:00 PM EDT  

Blogger Thomas Kyte said....

fluffy :) I like that....

Tue Oct 18, 02:09:00 PM EDT  

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