Re: The same session run on both instances (RAC), is it normal?

  • From: "Andrew Kerber" <andrew.kerber@xxxxxxxxx>
  • To: staywithpin@xxxxxxxxx
  • Date: Thu, 27 Sep 2007 12:52:07 -0500

That would be perfectly normal if it is using a preconnect type service.

On 9/27/07, qihua wu <staywithpin@xxxxxxxxx> wrote:
>
> select username, machine,  osuser, to_char(logon_time, 'YYYY-MM-DD
> HH24:MI') LG ,last_call_et
> from gv$session
> where username = 'GDBA_WUQIH'
>
> GDBA_WUQIH    ASIAPACIFIC\SCN7872    wuqih    2007-09-27 17:23    0
> GDBA_WUQIH    ASIAPACIFIC\SCN7872    wuqih    2007-09-27 16:40    0
> GDBA_WUQIH    ASIAPACIFIC\SCN7872    wuqih    2007-09-27 16:40    0
> GDBA_WUQIH    ASIAPACIFIC\SCN7872    wuqih    2007-09-27 17:23    0
>
> From the result, the session connects to two instances at the same time.
> it's amazing. Is it correct that a session connect to two nodes?
>
> On 9/27/07, LS Cheng <exriscer@xxxxxxxxx > wrote:
> >
> > I dont work with PL/SQL Developer so I am not sure what it does
> > underwood. But this is very easy to check
> >
> > select username, machine, module, osuser, to_char(logon_time,
> > 'YYYY-MM-DD HH24:MI') LG ,last_call_et
> > from gv$session
> > where username = 'GDBA_WUQIH'
> >
> > Thanks
> >
> > --
> > LSC
> >
> >
> >
> > On 9/27/07, qihua wu <staywithpin@xxxxxxxxx > wrote:
> > >
> > > select inst_id,count(*) from gv$session where schemaname='GDBA_WUQIH'
> > > group by inst_id
> > > 1    2
> > > 2    2
> > >
> > > And I have only two session through plsql devloper. Each of these
> > > sessions lands on both instances. That surprise me. One session sits on 
> > > both
> > > instance at the same time.
> > >
> > > On 9/27/07, LS Cheng <exriscer@xxxxxxxxx> wrote:
> > > >
> > > > please add a predicate for your user and not groupping at global
> > > > level because for a idle RAC system there are quite a few background
> > > > processes and RAC monitoring processes and if you have dbconsole then 
> > > > more
> > > >
> > > > thanks
> > > >
> > > > --
> > > > LSC
> > > >
> > > >
> > > >
> > > > On 9/27/07, qihua wu <staywithpin@xxxxxxxxx > wrote:
> > > > >
> > > > > I don't know why ask for groupping by inst_id, anyway the result
> > > > > is.
> > > > > select inst_id,count(*) from gv$session group by inst_id
> > > > > 1   36
> > > > > 2   39
> > > > >
> > > > > David may be correct that sid is not unique accross instance, but
> > > > > why gv$mystat will show non-zero stats value on both instances(since
> > > > > non-zeror statatics, that means the session operates on both 
> > > > > instance).
> > > > >
> > > > > Dan:
> > > > > a session connects to the database multiple times, it still has
> > > > > the same session id, otherwise they are not the same session, right?
> > > > >
> > > > > My question is "one session can only land on one instance during
> > > > > its lifetime?".
> > > > >
> > > > > Thanks very much for your reply. Have a good day.
> > > > >
> > > > > On 9/26/07, LS Cheng <exriscer@xxxxxxxxx> wrote:
> > > > > >
> > > > > > how about group by inst_id...?
> > > > > >
> > > > > > thanks
> > > > > >
> > > > > > --
> > > > > > LSC
> > > > > >
> > > > > >
> > > > > > On 9/27/07, qihua wu < staywithpin@xxxxxxxxx > wrote:
> > > > > > >
> > > > > > > We have a two nodes RAC, the strange thing is that many
> > > > > > > sessions run on both nodes.
> > > > > > >       select sid from gv$session group by sid having
> > > > > > > count(*)>1
> > > > > > > they are lots of rows return.
> > > > > > >
> > > > > > > My understanding for load balance is:  if sessions on instance
> > > > > > > 1 are too many, then new session will be connected to instance 2.
> > > > > > > But if at the beginning there were100 sessions on both inst1
> > > > > > > and inst2, after all the sessions on inst2 are completed, no 
> > > > > > > existing
> > > > > > > session on instance1 will go to instance2.
> > > > > > >
> > > > > > > But the fact of the above query told me some sessions run on
> > > > > > > both instance. How can this be true?
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>


-- 
Andrew W. Kerber

'If at first you dont succeed, dont take up skydiving.'

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