Arup,
Just picking up the thread on the BBWs. (Btw, I asked this question in this
list - never got an answer!) The following undocumented parameter limits the
numbe of CR copies in the Block buffers.
Name Value
--------------------------------------------- ------------------------------
Description
---
_db_block_max_cr_dba 6
Maximum Allowed Number of CR buffers per dba
What if there are more than 6 concurrent update requests for the same block.
Would that not result in BBW?
John Kanagaraj
Oracle Applications DBA
DBSoft Inc
(W): 408-970-7002
Disappointment is inevitable, but Discouragement is optional!
** The opinions and statements above are entirely my own and not those of my
employer or clients **
> -----Original Message-----
> From: Arup Nanda [mailto:orarup_at_hotmail.com]
> Sent: Wednesday, February 19, 2003 8:24 AM
> To: Multiple recipients of list ORACLE-L
> Subject: Re: Automatic Segment Space Management
>
>
> Jay,
>
> I have been using ASSM for last five months in our Datawarehouse
> environment. Haven't had a chance to play with the OLTP side, yet.
>
> Inserts are way faster as compared to system managed extent
> allocation. I
> read Don's article on DBAZINE. However, I would like to add
> one caveat here:
> ASSM does not *eliminate* buffer busy waits as the article claims; it
> *reduces* them. BBW occur due to concurrent access to a
> buffer by more than
> one session. This will be the case regardless of number of
> freelists. While
> ASSM eliminates the freelist contention - thereby reducing
> BBW in inserts -
> it does not reduce the likelihood that more than one sessions
> will try to
> get the same block to the buffer cache simulataneously.
>
> Table drops appear a little slower in ASSM; but that could be
> wrong - I
> never timed dropping a table in the system managed mode.
>
> HTH.
>
> Arup Nanda
>
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Wednesday, February 19, 2003 9:33 AM
>
>
> > I'm continuing to introduce myself to 9i. I've been reading about
> Automatic Segment Space Management, and I just wondered if
> anybody had any
> positive/negative experiences with it. I got some good info at:
> >
> > http://www.dbazine.com/burleson11.html
> >
> >
> > Thank you,
> >
> >
> > Jay Hostetter
> > Oracle DBA
> > D. & E. Communications
> > Ephrata, PA USA
> >
> >
> >
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Received on Wed Feb 19 2003 - 13:45:09 CST
