Re: Open_cursor setting

From: Donal Daly <ddaly_at_nl.oracle.com>
Date: Thu, 2 Jun 1994 12:25:36 GMT
Message-ID: <Cqrruo.H31_at_nl.oracle.com>


In article <CqoyMv.91E_at_cmutual.com.au>, aaj_at_cmutual.com.au (Tony Jambu) writes:
|>
|> In article <1994May24.091029.10510_at_wvnvms.wvnet.edu>, sh240031_at_wvnvms.wvnet.edu
|> writes:
|> > I have a question about the open_cursors parm in init.ora. Does anyone know
|> > the OS limit for this setting on a Sequent SE60 running Oracle 7.0.16.4.
|> >
|> > It was my understanding that the limit was 255; however, by increasing this
|> > value to 3500 allows us to supercede a bottleneck. Has anyone experienced
|> > a similar situation?
|>
|> While there is documentation to say that the limit is 255 (V6 I think), it is
|> undocumented that there is no hard limit in Oracle. I believe that it depends
|> on your Operating System and is very high.
|>
|> We have it about 500.

I don't believe there is an absolute limit to the total number of cursors any one session can have open at one time, if the following constraints are followed:-

  1. Each cursor requires virtual memory, so the total number of cursors would be limited by the amount of memory that process can address. (Have a look at the output from ulimit -a (SVR4))
  2. The limit specified by open_cursors parm in init.ora

Having open_cursors set to 3500 seems awfully high, but I guess it would depend on your application. You should check how many need to be opened at any one time, as depending on the main memory available on the machine, you might induce paging and swapping, which would naturally reduce performance.

-- 
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 Donal Daly, (ddaly_at_ie.oracle.com)                                 Olivetti PLD
 Oracle Europe, Blackrock, Co. Dublin, Ireland
					
 Any opinions expressed above are my own!
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Received on Thu Jun 02 1994 - 14:25:36 CEST

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