Logon Group in a Cluster

[Former Member]

Hi,

I have CI - 02 on one host and dialog instance -03 on another host.

I have created a logon group by name public and assigned these 2 instances.

My question is if one instance got down how the user will automatically switch over.

It's cluster environment already installed.

Let me know if u need information.

Regards,

Saravanan.S

[Former Member]

Hi,

If I undestand correctly, you have a CI on cluster (MSCS ?) and a SA on a third host.

Your logon group includes both the CI and the SA.

It means that your users are, eithe connected on the CI or the SA.

With this architecture, you don't have High Availability.

If you user is connected on the CI and there is a cluster fail over, the user will be disconnected if the CI node failed.

If your user is conencted on the SA and there is a SA failure, the user is disconncted.

For HA, it's better to have at least 2 SA on 2 different hosts and to include only the 2 SA in the logon group.

Regards,

Olivier

[Former Member]

Hi,

What u mean by SA?.

I have CI on one node and dialog on other node with MSCS.

Enque replication servers installed locally.

Let me know how to define the logon group.

Regards,

Saravanan.S

[Former Member]

Hi,

Sorry, SA should have been AS = Application Server = DI = Dialog Instance

Regards,

Olivier

[Former Member]

Hi Olivier,

thanks for your reply.

SO u mean to say I need to install another DI.

In that case I can install on a different host other than MSCS?.

Then I have to define the logon group right....

Regards,

Saravanan.S

[Former Member]

Hi,

Don't install a DI on the cluster. It is not a recommended setup.

DI are Single Points of Failure. It means that you need at least 2 of them on 2 different hosts to get High Availability.

Regards,

Olivier

[Former Member]

Hi Olivier,

thanks for your update.

I followed exaclty the steps described in the SAP Installation Guide under High Availability.

Now 2 Hosts in a cluster with central and DI wont give High availability.

Anyways i'm trying your solution of intalling DI in 2 different hosts.

Regards,

Saravanan.s

[Former Member]

Hi Olivier,

Sorry for the late resposnse.

Went out for a vaction.

Now I have installed 2 DI outside of MSCS.

define logon groups for the 2 DI as public.

when i login under the group, and shut down one di the users are not automatically switch over.

I tried ensmon.exe and got replication is active as message.

Let me know how to proceed further.

Regards,

Saravanan.S

[Former Member]

Hi Saravanan,

>when i login under the group, and shut down one di the users are not automatically switch over.

This is nominal. If you stop one DI, all the users conencted to it are disconnected but they can reconnect immediately to one of the remaining DI.

Don't believe that High availability is something magical !

Regards,

Olivier

[Former Member]

Dear olivier,

I need a solution like if users are connected to one instance, if we stop that instance the users has to move to the next available AS.

This is not possible?

Then what is the use of Cluster functionality then?

Regards,

Saravanan.S

[Former Member]

Saravanan,

If you need the impossible then you are in trouble !

The purpose of a cluster and several DI is that, in case of failure, users are able to reconnect almost immediately.

For RFC calls the service interruption is virtually invisible.

The availability of SAP running on a cluster is higher than without a cluster, that is why it is called a

high availability solution and not an absolute availability...

Regards,

Olivier