Re: Oracle on windows and shadow thread file access

Jeremiah

I _did_ say the background oracle 'processes' meaning lgwr,dbwr,ckpt threads on Win32 specifically. My understanding from the question was that he was wondering whether each user's process in a dedicated-server configuration opened all of the datafiles too

....but I might have mis-understood the question.

On Fri, 29 Nov 2002, Jeremiah Wilton wrote:

> On Fri, 29 Nov 2002, Jeff Herrick wrote:
>
> > None...only the oracle background processes (threads in Winblows)
> > access the datafiles/logfiles etc. All other communication is
> > done through the SGA. On some Unix variants you _can_ reach
> > a file_open max kernel parameter because each process (in a
> > dedicated server scenario) opens it's own stdin/stdout/stderr.
> > I guess the same could be true of processes running under
> > windows too. So in the limit...you could hit a wall but only
> > due to the per-process overhead.
>
> Uh, I'm probably not going to be the only one to point out this isn't
> true. I don't know about Win32 thread architecture, but in Unix and
> unix-like operating systems, the shadow (server) processes each open
> whatever files they need for write. It is true that they also open
> the shared memory segments in order to write and read from the SGA,
> but they do the reading from disk. Otherwise, which process do you
> think is reading from the datafiles?
>

[snip]

> > On Fri, 29 Nov 2002, Grant Allen wrote:
> >
> > > Saw an interesting post in comp.databases.oracle.server postulating that if
> > > a shadow thread needed an open file handle on all files in a instance (or
> > > even some of them), the process handle limit in windows could constrain user
> > > scalability (e.g. too many users would result in ora-12500 unable to spawn
> > > errors and the like). (Let's ignore MTS/shared server mode for the moment)
> > >
> > > Sounded interesting, but I thought I'd ask if anyone knows whether a shadow
> > > thread (or process under unix) does open a handle on each file (control,
> > > data, redo), some of them, or none of them?

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