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We posted a new article to the site today from first time author Gaurav Sharan Gupta. I wanted to get a thread started on the article to get some feedback and thoughts on the article. Did you find the information helpful? Do you have any suggestions for improvement? Would you like to see additional articles on the same topic/different topics from Gaurav?
Here's the URL for the article:
Oracle 8i Row Chaining and Migration
http://www.dbasupport.com/oracle/ora...chaining.shtml
had a quick read
article states that oracle block size starts from 512 bytes, wrong it starts from 2K (minimum)
pctused definition is totally wrong, pctused is used for DELETEs not INSERTs, a block is removed from freelist when it reachs PCTFREE, re-enters to freelist when block usage falls BELOW PCTUSED
Some definition is easy to get confused, PCTFREE is for when the block will be removed from the freelist, PCTUSED is for when the block will be put back to the freelist.
The author has totaly confused the roles of PCTFREE and PCTUSED parameters. What we have:
PCTFREE = 20, PCTUSED = 55
We inserted 6 rows, each consuming 10% of the net block size, so 60% of block is occupied. Block will remain in free list, not being removed from it as the article claims. Now we updated one of the rows, increasing its size from 10% to 25% of the block size. So now we have 75% of block occupied. 25% of space is still available for future updates, no? Not according to the author. He claims that another update wich would require another 10% of the block space will fail!?!? He has got confused some basic concepts about PCTFREE and PCTUSED. He obviously belive that each increase of the row size by the update takes space only from the PCTFREE reserved area. However this is totaly wrong. Updates has all the free space in the block availbale, it is inserts that are blocked by the PCTFREE size. Even after that update block is still available for inserts, as we still haven't reach PCTFREE.
So the correct behavior in the author scenario would be:
The second update will occupy another 10 units of the block, and the row will remain in that block in one piece, leaving 15% of block still available to future updates. However at that moment block will be removed from free list, as there is less free space available (15%) than it was specified with PCTFREE.
Now even next update which requires 10% of additional space will succeed without the row chaining. Only if we try another update demanding another 10% space, Oracle will need to chain that updated row, moving its contents into another block.
I can't help myself not to state: The article is a failure, it gives a totaly wrong description of the basic concepts regarding PCTFREE and PCTUSED. And if you don't understand those basics you can't realy understand what row chaining/row migration realy is and what is causing it.
No offence to anyone....
I want to say thanks to everyone for their comments. The author has been forwarded the comments as well as a link to this thread, so I'd like to give him a chance to respond before making necessary changes to the article.
Please tell me this isn't the same person who authored those terrible 'performance' lessons.
- Chris
Completely different author, but a couple similarities -- 1) both really want to contribute to the Oracle community by helping others, and they've taken it upon themselves to do so by writing these articles for free; and 2) they want and encourage feedback on their articles to make them as accurate as possible.
Note: Post edited to remove original comments made in bad taste. Apologies to those who may have taken offense at the poor choice of words used.
Little bit more information about article:
Autor(s) has to know that OS (not oracle) block size depend not from OS itself but from
filesystem in this OS (mkfs command). 512 bytes in solaris isn't correct information too.
Forrest,Quote:
Originally posted by fstroud
Completely different author, but a few similarities -- 1) both are from India and are not entirely comfortable with the English language; 2) both really want to contribute to the Oracle community by helping others, and they've taken it upon themselves to do so by writing these articles for free; and 3) they want and encourage feedback on their articles to make them as accurate as possible.
They'd be kinda perplexed on that poor english defence you've taken on their behalf. We have some active members here from all origins(Re-Edited it!Don't mean to hurt no-one and don't want this thread to go off tangents either)who write horrible english but make sense regarding explanations.
I don't really know if it's a smart idea to first post your stuff and then ask for a review because it'll be shredded first and read later.
Cheers!
Tarry
[Edited by Tarry on 09-26-2002 at 06:59 AM]
Pls Don't generalize...Quote:
Originally posted by fstroud
Completely different author, but a few similarities -- 1) both are from India and are not entirely comfortable with the English language; 2) both really want to contribute to the Oracle community by helping others, and they've taken it upon themselves to do so by writing these articles for free; and 3) they want and encourage feedback on their articles to make them as accurate as possible.
I HAVE SEEN WESTERN PEOPLE WITH HORRIBLE WRITING
SKILLS.......THAT TOO ENGLISH BEING THEIR MOTHER
TOUNGE...
What are the plans for the "Performance" series? I wouldn't think that you could let it stand as it is, with so many errors in it.
slimdave, the Performance series is on hold as the author works on revisions. He hasn't given a timeline on when he expects to have those revisions completed.
bang_dba, I apologize for making that generalization in my earlier post. I also don't want to speak for the authors too much, so I'll hold off until I hear more from them, specifically from Gaurav.
I understand that these folks are trying to help the general community - as are many of us on these boards. I also understand that they are making an effort to put these articles together, as are, again, many of us who put the effort in on these boards. I also understand that it takes 'guts' to put your thoughts out there for the world to see and critique, so they should be given some leeway for making the attempt.
Understanding all this and knowing how difficult that actually is does give me some amount of sympathy for them
But only a small amount. There are a lot of very bright people on these boards. There have been a lot of very good discussions here. There is also a lot of good information elsewhere.
So to put up an article on this sight without at least knowing the fundamentals of what you are addresssing seems foolish at best.
If somebody gives a wrong answer in this forum, there are usually ten people there to correct them. If one reads through an entire thread, one usually ends up with the right answer and, quite often, a better understanding of the problem. However, that takes a good bit of work on the part of the reader as well.
An article makes it easier on the reader, and so article must be held to a higher standard. The reader does not get the benefit of multiple views on the subject and does not get to see what other people think of the solutions. They generally assume that the author knows what they're talking about, so the solutions presented must be correct.
Therefore, when such an article is fundamentally flawed, as in this latest article, or wildly innaccurate, as in the performance articles, this actually *hurts* the community at large instead of helping it.
1 - If you are going to write an article, have some knowledgeable people check it *before* posting it anywhere real.
2 - If DBASupport.com is really trying to help the community, then they should do the same - have someone knowledgeable check the article before it is posted.
Otherwise,
1 - Some people will be led astray
2 - Once word gets around, the credibility of the author is shot. Which is how I (and I'm sure, many others) feel about the author of that performance series. There is no point in 're-working' the article. This person has already shown that he knows virtually nothing about performance, and has no problem in publishing garbage that is blatantly un-true. So, since I already know that half of what he already published was complete garbage, do you honestly think I'm going to use the 're-worked' article as a source for figuring out things I *don't* know? Please.
3 - The credibility of the web-site can be damaged as well. A lot of people now know about the fiasco with the performance series and that it was posted *here*. Now this latest article and all its issues are posted here as well. Credibility is one of those things that, while it certainly seems hard enough to build once, it is doubly hard to build a second time. Now, I'm not saying that this has hurt the site much, if at all...yet. I'm just saying that we might want to be a little more careful is all.
So, I do apologize for my original glib remark. However, I do feel strongly about protecting against the proliferation of bad information, and am hard-pressed to have sympathy for those that get caught doing it.
- Chris
I couldn't agree more with what Chris has said.....
As an author of a couple of articles on dbasupport.com, I do agree with Chris. Although my articles are "How to.." type articles and I don't enforce my article as being the ONLY way to perform the function, they are only SUGGESTIONS. I do find it important to give correct information to people with similar issues.
Cheers,
quote:
--------------------------------------------------------------------------------
Originally posted by fstroud
Completely different author, but a few similarities -- 1) both are from India and are not entirely comfortable with the English language; 2) both really want to contribute to the Oracle community by helping others, and they've taken it upon themselves to do so by writing these articles for free; and 3) they want and encourage feedback on their articles to make them as accurate as possible.
--------------------------------------------------------------------------------
Disappointing remarks..
[Edited by patel_dil on 09-26-2002 at 08:28 PM]
I too agree with chris.I am a new dba and I relay on dba support articles but after reading this thread I lost my faith on forums I was in the impression that these articles are double checked by some knowledgeable dba gurus.
There's no need to lose faith.Quote:
Originally posted by ashoo
I too agree with chris.I am a new dba and I relay on dba support articles but after reading this thread I lost my faith on forums I was in the impression that these articles are double checked by some knowledgeable dba gurus.
How are you going to layout your path to learn and then enhance your knowledge, that's the question.
You should and so do most of the renowned database experts say is read the manuals(starting with the concepts manual) written by the vendor(which also requests you as a reader to correct them). and besides the "Oracle does this or that" (which you too must try to fathom), the rest is all for you to try it out and see if that's the way is works as it says.
Bad Information can be disastrous.
Cheers!
How do you upload articles without checking its contents?Quote:
Originally posted by chrisrlong
1 - If you are going to write an article, have some knowledgeable people check it *before* posting it anywhere real.
2 - If DBASupport.com is really trying to help the community, then they should do the same - have someone knowledgeable check the article before it is posted.
Being a administrator, I feel your way of writting is much surprising than the contents of article...Quote:
Originally posted by fstroud
Completely different author, but a few similarities -- 1) both are from India and are not entirely comfortable with the English language; 2)
Sameer
[Edited by Sameer on 09-27-2002 at 09:21 AM]
I have no idea what the submission process is for this site, however... One would think that the process could be:Quote:
Originally posted by Sameer
How do you upload articles without checking its contents?
- Click on some 'submit' button somewhere
- This puts it in a page somewhere on the site. However, this page is not linked from anywhere on the site but a special forum.
- The act of submission automatically makes an entry in a special forum set up specifically for article reviews.
- How one determines who has access to that forum has to be determined. Most likely they would be chosen by the Admins/SuperAdmin. In any case, only maybe 20 or so people are probably necessary. Then again, maybe everybody has access - whatever.
- This special forum also has voting enabled.
- Then, a process must be developed. Maybe:
- An article's entry, which contains the link to the article sits in that forum for maybe 2 weeks.
- During that time, some members of that special forum are expected to read and evaluate the article.
- They then reply to the thread with comments and criticisms and vote 'yes or no' whether the article is fit to publish as-is.
- If, at the end of those 2 weeks, at least, say, 10% of the replies have voted 'no', then the article goes back to the author for re-work.
- If less than 10% vote 'no', then the article is published.
- In either case, the thread is locked or deleted so as not to confuse everyone. If and when the author re-submits, another thread is automatically opened.
Mind you, I have absolutely no experience running a web-site and I am also not trying to volunteer myself for anything :D. This just occurs to me as one way to solve the problem.
- Chris
Chris, great ideas for future articles -- we will use many if not all of them for article submissions that come in from now on. I'll work on putting the details together on our end.
Thanks for your feedback and suggestions.
Cris, I agree, This is great idea.
Whis this procedure may be i will write some articles to forum.
The author of the RM/RC article has sent in a revised version of the article, which will be posted to the site shortly. Gaurav wants to thank everyone on this thread for their comments and suggestions.