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Yeah, I'm pretty sure hrishy is aware of what Chaining/Migration is and it's effects. The questions was more, Why was a pointer maintained in the original block. Hence the discussion.
Cheers,
OCP 8i, 9i DBA
Brisbane Australia
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Originally posted by grjohnson
Another sign of a good DBA: Might not know the answer, but knows where to find it. Very important...
This is perhaphs the number one skill that i would look for in any DBA
regards
Hrishy
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Yeah .
I mistook it as a separate Q.(when row migration takes place)
Cheers
K.Chithra
Oracle DBA
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Re: interview question perhaphs :-)
Originally posted by hrishy
Hi
2)when you have row migration why does oracle keep a pointer in the block to the row where it has moved now ?
regards
Hrishy
I belive this reason cud be the one of the reasons....
after Insert of data....a pointer pointing to memoray location is assinged to it.
after deletion of data....the pointer is dropped and not actual data is deleted, as writing 0 on disk takes too much time & unnecesssary use of resources.....
So if we think logically, and i AFAIK Oracle is wrriten in C to handle the memory allocation and deallocation part, Pointers to memory location can be assigned or dropped and can be updated but requires complex logic.......instead Pointer to Pointer wud be more flexible and easy....so when a row is migrated...a new pointer is assigned......
Correct me if i am wrong.......
Abhay.
funky...
"I Dont Want To Follow A Path, I would Rather Go Where There Is No Path And Leave A Trail."
"Ego is the worst thing many have, try to overcome it & you will be the best, if not good, person on this earth"
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Originally posted by k.chithra
Yeah .
I mistook it as a separate Q.(when row migration takes place)
Cheers
No worries... I do it sometimes as well, skim the question and then answer.
OCP 8i, 9i DBA
Brisbane Australia
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