| Why do they know about the space of leaf block? [message #272829] |
Sun, 07 October 2007 23:21  |
trantuananh24hg
Messages: 744
Registered: January 2007
Location: Ha Noi, Viet Nam
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Senior Member |
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Dear all!
This image above describes the cost and benefit of coalescing index method. However, I wonder about the space of leaf blocks was merged to free up which is estimated or calculated by 50% of the first and the second one. The behind B-Tree Index was coalesced, and I knew.
According to the dba_indexes data dictionary, I tried to find the formula to calculate them, but I did not.
Can you explain to me?
Thank you very much!
[Updated on: Sun, 07 October 2007 23:22] Report message to a moderator |
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| Re: Why do they know about the space of leaf block? [message #272832 is a reply to message #272830] |
Sun, 07 October 2007 23:48  |
trantuananh24hg
Messages: 744
Registered: January 2007
Location: Ha Noi, Viet Nam
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Senior Member |
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@anna!
First time, I wish the best to you, and thank you for your pleasant comparing between Coke and Pesi, but I'd like to drink fruit.
Of course, the cost and benefit between Rebuild and Coalesce Index are different, then I know about them.
Assuming I has only one storage which contained my datafile, and only one tape to backup, it's absolutely to consider about the indexes, especially large index. So, when using Rebuild Index, I may abide by Oracle Reference
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Higher cost: Require more disk space
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Using Rebuild Index method, I have got effective one..
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Can change storage and tablespace parameters without having drop original index.
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However, I am only a newbie on Oracle environment, like a child gets inquisitive everything around him, when I saw this image, I were surprise and asked myself : "How do they calculate exactly the leaf block space and show it in?". Is there any formula to guess, estimate or do anything else to generate result.
Again, thank you, Ms anna, both of your answer and your article named as "Drop OEM to avoid Database hang".
[Updated on: Sun, 07 October 2007 23:49] Report message to a moderator |
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| Re: Why do they know about the space of leaf block? [message #273099 is a reply to message #272844] |
Tue, 09 October 2007 01:53 |
trantuananh24hg
Messages: 744
Registered: January 2007
Location: Ha Noi, Viet Nam
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Senior Member |
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Dear!
I have read the Index document below, however, I've not understood about somethings like that "50-50 split block", "90-10 split".. and how did he found the index header section.
Would you like to teach me more?
Additional question: In your situation, how do you identify which indexes will be rebuilt or coalesce?
Thanks for your reply!
[Updated on: Tue, 09 October 2007 02:01] Report message to a moderator |
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