Virtual Hostnames and RAC on Exadata

[Former Member]

Hi

Our project is installing a number of SAP products (ECC, SRM, Sourcing, etc) across a number of environments (development, test, training, etc). We plan to deploy the database components of all these systems using a RAC cluster on an Oracle Exadata machine running Oracle 11.2.

Executing the "hostname" command on the Exadata box returns a long fully qualified domain name that is longer than 13 characters. To get around this, and to isolate the installation from the underlying physical hostname, we plan on using virtual hostnames (as described in SAP note 962955), but we are unsure of the best approach.

Should we configure a virtual hostname for each installation of each product for each RAC node? This will lead to a multitude of virtual hostnames (~100), but offer us maximum flexibility. Due to our network deployment, this might also require additional network configuration (routing, VLAN configuration, etc).

Or should we configure just a single virtual hostname for each node? This would be the minimum number of virtual hostnames required.

Or do we not need virtual hostnames at all? Does RAC and the Oracle Scan Listener offer a similar capability.

Any insight on this topic would be appreciated.

Thanks

[Former Member]

Hi, David.

Even though, you’ve got our answer directly, I’d like to clarify your question for SAP community not leaving it unanswered.

Hostname less than 13 characters is the absolute must for SAP environment and as you correctly stated “hostname” command has to return hostname with no domain in it. It is not a problem to configure Exadata database nodes without domain name in hostname, just need to make sure installation worksheet filled in for ACS engineers who’s doing initial configuration states non-FQDN hostname in database nodes hostname fields. Default Exadata installation has FQDN hostnames, but it can be changed to non-FQDN if required at any later point.

As for virtual hostnames stated by 962955, yes, correct, they are normally used in non-RAC environment as layer of abstraction and separation. In Real Application cluster virtualization of hostnames taken by Clusterware VIPs and no further layer for abstraction is required. VIPs are foundation of main concept of RAC architecture, if one db node is down, Clusterware takes care for relocation of given vip's sessions to the other nodes. At the same time SCAN listener is aware about those VIPs and supposed to redirect client connections across available nodes using Clusterware VIP names all the time cluster works supporting workload distribution and high availability capabilities.

Considering above, it doesn’t make a point to add extra layer on top Clusterware’s VIPs and increase complexity of database cluster configuration. More over worldwide experience of RAC customers says that typical installation of SAP on top of Oracle Real Application Cluster does not use virtual hostnames for database tier other than Clusterware VIPs.

Hope answer above is helpful and answers the concern.

Regards,

Evgeny

[former_member371029]

Hi Evgeny,

we are having a similar problem in our project, where we need to install the SAP database on a running Exadata with non-SAP databases on it.

This Exadata machine will not have the SCS on it, only databases (and BR*Tools,if we can't put them outside).

This Exadata was configured sometime ago by ACS using the FQDN as hostname.

Situation is that this is a productive machine, with live databases running and the customer does not want to adapt the hostname for SAP purposes, mainly, because doesn't know the impact of this change in the running non-SAP databases.

As you mentioned that the default FQDN hostnames could be changed at a later time to non-FQDN, I wonder if this change has an impact on the databases, how difficult or easy it is, or if there is any workaround for this limitation on a pure database server.

Appreciate any help you can provide.

Thanks.

Joao

[fschoen]

Dear All

Wouldn't it be enough when you just set the environment variable SAPINST_USE_HOSTNAME to the non-FQDN before you start the SWPM?

regards

fabian