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

Hi, thanks everyone here for show your idea and thinking here.

Finally I am sure the two sessions shown on two instances are because I queried gv$view, and gv$view will spawn parallel session on different instances to return the information on each nodes, so that's why I saw there is one session for each nodes.

Thanks Nilo Segura,
Your inforamtion is very useful to learn RAC.

Thanks,
Qihua

On 9/27/07, qihua wu <staywithpin_at_gmail.com> wrote:
>
> Hi, Nilo, thanks for your reply. But I didn't configure the method
> parameter.
> test =
> (DESCRIPTION =
> (SDU = 32768)
> (enable = broken)
> (LOAD_BALANCE = yes)
> (ADDRESS =
> (PROTOCOL = TCP)
> (HOST = server1)
> (PORT = 1525)
> )
> (ADDRESS =
> (PROTOCOL = TCP)
> (HOST = server2)
> (PORT = 1525)
> )
> (CONNECT_DATA =
> (SERVICE_NAME = test)
> )
> )
>
> This time I query again against gv$mystat. It shows two different sid now.
> When I queried it this morning, the number of the two sid were the same.
> SQL> select unique sid from gv$mystat;
>
> SID
> ----------
> 542
> 550
>
> On 9/27/07, Nilo Segura <nilosegura_at_gmail.com> wrote:
> >
> > No, there is an option such that the client will connec to both
> > instance(s) at the same time. In the normal case, you are connected to one
> > instance, then will failover to the other instance(s). It is what Andrew
> > Kerber mentioned in his post..
> >
> > Check the connect string being used. The keywork to look for is
> > FAILOVER_MODE ... here is a snipet of the oracle doc. See the
> > METHOD -> PRECONNECT...
> >
> > This can explain what you see..
> >
> > FAILOVER_MODE Subparameter Description
> >
> > BACKUP
> >
> > Specify a different net service name for backup connections. A backup
> > should be specified when using preconnect to pre-establish connections.
> >
> > TYPE
> >
> > Specify the type of failover. Three types of Oracle Net failover
> > functionality are available by default to Oracle Call Interface (OCI)
> > applications:
> >
> > -
> >
> > session: Set to failover the session. If a user's connection is
> > lost, a new session is automatically created for the user on the backup.
> > This type of failover does not attempt to recover selects.
> > -
> >
> > select: Set to enable users with open cursors to continue fetching
> > on them after failure. However, this mode involves overhead on the client
> > side in normal select operations.
> > -
> >
> > none: This is the default. No failover functionality is used. This
> > can also be explicitly specified to prevent failover from happening.
> >
> > METHOD
> >
> > Determines how fast failover occurs from the primary node to the backup
> > node:
> >
> > -
> >
> > basic: Set to establish connections at failover time. This option
> > requires almost no work on the backup server until failover time.
> > -
> >
> > preconnect: Set to pre-established connections. This provides
> > faster failover but requires that the backup instance be able to support all
> > connections from every supported instance.
> >
> > RETRIES
> >
> > Specify the number of times to attempt to connect after a failover. If
> > DELAY is specified, RETRIES defaults to five retry attempts.
> >
> > Note: If a callback function is registered, then this subparameter is
> > ignored.
> >
> > DELAY
> >
> > Specify the amount of time in seconds to wait between connect attempts.
> > If RETRIES is specified, DELAY defaults to one second.
> >
> > Note: If a callback function is registered, then this subparameter is
> > ignored.
> >
> >
> >
> > > --
> > > > > Nilo Segura
> > > > > Oracle Support - IT/DES
> > > > > CERN - Geneva
> > > > > Switzerland
> > > >
> > > >
>

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