Re: Oracle on windows and shadow thread file access

On Friday 29 November 2002 08:43, Jeff Herrick wrote:
> 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

Maybe not all of the data files, but the users dedicated server process will open datafiles as needed to read data into the block buffer.

Now I don't know if I've helped any, or just added to the confusion.

Jared

> ....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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