Re: Oracle sessions/proccesses

Richard Stanton wrote:

> Hello
>
> I am running Oracle 8.05 on nt.
>
>
> Can anyone explain to me the relationship between Oracle sessions and
> processes?
>
> Is it 1 connection to the database = 1 process?

Not necessarily. Try doing a select * from sales parallel 8. One connection, 9 processes.

That's just one example.

The other way holds true as well. In multi-threaded server configurations, one hundred connections could be causing just a couple of processes to be used (dispatchers and shared server processes).

>If so, then why in
> Instance
> Manager do the two not tally up? For example, there are currently 34
> sessions listed - 26 from the application, 7 background and the
> session I am using. However, when I switch to the Resource limit tab
> it lists 35 sessions and 61 processes. So what are these extra
> processes?
>

Are you using the Enterprise Manager console? Then the Intelligent Agent counts as another session. Just for starters.  

> We sometimes hit the max number of processes. What are the
> implications to the database performance if I increase the limit,
> currently set to 100?

There are a lot of implications, because processes is one parameter that is used by others to determine their limits unless otherwise explicitly set. You'd have to trawl through tahiti.oracle.com, which contains a complete list of init.ora parameters, to find them all.

>
> Hope that all makes sense
>
> thanks
>
> Richard

I've been a a bit vague in my reply, largely because it's just gone midnight. But there is no one-to-one correspondence between users, sessions and processes. It can get horribly complicated by things I'm sure you'll say you're not using, such as CMAN, MTS, the Intelligent Agent, Parallelism (explicit or implicit) and so on. Thing is, there's a lot of factos to affect the numbers. I wouldn't worry about whether the numbers tie up precisely, but I would be doing some research on the implication of increasing the processes parameter. You certainly don't want to set it to some ridiculous sky-high value, just a modest increase from what you've currently got, because obviously 100 is not sufficient.

Regards
HJR

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