Re: Please define ROW CHAINING!!!
Date: 1995/09/29
Message-ID: <44hujn$ar2_at_dingo.cc.uq.oz.au>#1/1
Judie Stroup <stroup_at_Ops195.LMSC.Lockheed.Com> wrote:
>snowden_at_haven.ios.com (Roger Snowden) wrote:
> >Row Chaining is the method whereby Oracle tracks block overflows. Oracle
>>rows are variable length by design, although they may be fixed length in
>>practice. Since Oracle permits variable length columns (varchar, etc.),
>>it needs a way to allow a row to be moved if it no longer fits into a
>>block. A new block is allocated and the row plopped there, with a
>>forward pointer to it. It is a linked list.
>>
>>Not very efficient, so you want to avoid it when possible.
>>
>>Roger Snowden
>>snowden_at_haven.ios.com
>>snowdenr_at_boystown.org
>>
>Actually, I think this is what Oracle calls a "migrated" row. Chained rows
>are where the entire row it too large to fit in a single database block and
>therefore must always be stored in more than one block. Migrated rows can be
>fixed, but chained rows cannot (unless you want to change your database block
>size or shorten the row). They both have the same performance problems.
>judie
>stroup_at_ops195.lmsc.lockheed.com
Judie hit the nail right on the head....
-----------------------------\ooOoo/----------------------------------- Gordon Hooker MACS PCP ,--_|\ 25 Clarke Street, Ripley, Queensland, 4306, Australia / \ gordonh_at_acslink.net.au \_.--._/ mobile: 018883835 phone: 61-7-2889716 V -----------------------------------------------------------------------It is far better to remain silent and appear a fool, than to open ones mouth and remove all doubt... Received on Fri Sep 29 1995 - 00:00:00 CET