Re: Checking if a RAC database has one or more node down

From: Mladen Gogala <gogala.mladen_at_gmail.com>
Date: Fri, 17 May 2019 10:13:19 -0400
Message-ID: <4cdfc502-af46-804f-e5d5-4f8902e25394_at_gmail.com>



Essentially, RAC cluster is a dynamic thing. Instance can join the cluster, leave the cluster or even be evicted. Granted, evictions are much less frequent these days than with the previous releases, but they still do happen. A RAC cluster is comprised of the instances which are currently in the cluster. When an instance leaves the cluster, there is no certainty that it will ever come back or the administrator may even use srvctl to remove the instance. When an instance joins the cluster, a reconfiguration will happen in order to distribute the lock resources between the nodes. Cluster only knows about the current instances comprising it. Not just that, if your CRS are deployed on more than 2 servers, it is entirely possible to have the servers sub-divided into server pools and have different databases running om separate server pools.

On 5/17/19 8:52 AM, Ls Cheng wrote:
> Hi
>
> How do we know the desired count of instance?Just because someone says
> so or it can be obtained from somewhere? In your example
> of cluster_database_instances is 8 but gv$instance returns 4 how do
> you know 4 is the desired count?
>
> BR
>
>
>
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>
> On Fri, May 17, 2019 at 2:46 PM Luis Santos <lsantos_at_pobox.com
> <mailto:lsantos_at_pobox.com>> wrote:
>
> Thanks for all replies!
>
> Let's dig into my need. When I said /just SQL/ I mean that my need
> is to know if a RAC node is down while connected, and just
> connected, to the database. No matter the node. Of course I'm
> aware of srvctlou crsctlcommands, but they are out of my need scope.
>
> And querying GV$INSTANCEalone will no work. If a node is down it
> will be missing from GV$INSTANCE, but how much nodes is my goal?
>
> Digging again: I'm talking about a simple monitoring script. With
> no human (/or AI robot/) DBA querying.
>
> Up to now I have been using, with relative sucess, the comparision
> of count(*) from GV$INSTANCEto the value of
> cluster_database_instances database parameter.
>
> But now we have a Exadata machine with 8 nodes, but with only 4
> nodes actives for a specific RAC database. The count(*)from its
> GV$INSTANCEé 4 and the value from
> cluster_database_instances parameter is 8.
>
> So, my qustion again: is it possible to design a simple query,
> while connected to RAC databases, to show if one (or more) node(s)
> from the, let's say, desired count of instances, is missing?
>
> /
> /
> /--/
> /Att/
> /Luis Santos
>
> /
> /
> /
>
>
> Em qui, 16 de mai de 2019 às 23:22, Suresh Rajagopal
> <sureshr7_at_gmail.com <mailto:sureshr7_at_gmail.com>> escreveu:
>
> crsctl stat res -w "TYPE = ora.database.type"
>
>
>
> On Thursday, May 16, 2019, 2:45:29 PM PDT, Mark W. Farnham
> <mwf_at_rsiz.com <mailto:mwf_at_rsiz.com>> wrote:
>
>
> select inst_id,status from gv$instance;
>
> *From:*oracle-l-bounce_at_freelists.org
> <mailto:oracle-l-bounce_at_freelists.org>
> [mailto:oracle-l-bounce_at_freelists.org
> <mailto:oracle-l-bounce_at_freelists.org>] *On Behalf Of *Luis Santos
> *Sent:* Thursday, May 16, 2019 4:51 PM
> *To:* ORACLE-L
> *Subject:* Checking if a RAC database has one or more node down
>
> Is there a way, using just SQL when connected to a RAC Oracle
> database (whatever the version), to check if all nodes are up
> and runing?
>
> /--/
>
> /Att/
>
> /Luis Santos/
>
> //
>
>
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-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217


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Received on Fri May 17 2019 - 16:13:19 CEST

Original text of this message