Re: ASSM bug: slow INSERT after uncomitted DELETE

"ca111026" <ca111026_at_gmail.com> wrote in message news:d4a0b7a5-aa4e-41bc-9adb-ecd251c56019_at_g1g2000pra.googlegroups.com...
> Sorry, how buffer busy waits are related to ASSM? I thought buffer
> busy waits ('read by other session' in later versions) is event that
> happens when multiple sessions are reading the same block from memory.
> This is why it is called 'buffer' (from 'buffer cache'). If table is
> "narrow" i.e. rows are short then there will be many rows per block,
> ASSM or no ASSM.
>
>
>

There are several causes of "buffer busy waits". They can also appear when two people want to modify the same block at the same - and if you have a table with freelists = 1, then there is only one insertion point available at a time, so concurrent inserts can see buffer busy waits.

There's a lot that could be said about multiple freelists, multiple freelist groups, ASSM, and RAC at this point and the various pros and cons of different technologies - but essentially ASSM was introduced to hide a common problem instead of instructing people about an existing solution.

-- 
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html

The Co-operative Oracle Users' FAQ
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