HA Installation on AIX 6.1 / Oracle 10.2.0.4

[Former Member]

Dear Experts,

I need to do HA installations for ECC / EP / CRM / BIW production servers. Our OS is AIX 6.1 with Oracle DB.

Our Production Landscape Outline:

Node1 & Node2 in cluster & 2 application servers for dialog instances.

I have asked OS team to create mount points as described below:

/sapmnt/PRD - NFS (Global, to be available on all 4 servers i.e. Node1 / Node2 / APP1 / APP2.

/usr/sap/trans - NFS (Global, to be available on all 4 servers i.e. Node1 / Node2 / APP1 / APP2.

SAP_VG: Node1 virtual host name - ECCPRD

/usr/sap/PRD - To be available on Node1 on which ASCS+CI will run.

/usr/sap/PRD/ASCS00 - To be available on Node1 on which ASCS+CI will run.

DB_VG: Node2 virtual host name - ECCDBA

All oracle mount points - To be available on Node2 on which Oracle DB will run.

In case of any node failure, the respective VG should move to the other node & start the services there.

Now, the OS team says that the scenario that I have stated above is not possible, as in case of any 1 node failure, the other node cannot represent 2 virtual host names.

Please help me understand this HA installation concept & the virtual host name requirements for HA installation on AIX.

Regards,

Ashish Khanduri

[sunny_pahuja2]

Hi,

First of all, one thing more that you need to take care:

If your ECCPRD node will be down on which ASCS+CI will run then your ASCS resources will move to second node. At that time your CI will not move to second node as CI is no more point of failure only message server is single point of failure. In that case on DB node i.e. ECCDBA, you need to install Dialog instance. So, when failure will occur from ECCPRD to ECCDBA then your Dialog instance on ECCDBA will take services of CI.

So, you need to create local file system /usr/sap/<SID>/D<instance no.> on ECCDBA and /usr/sap/<SID>/DVEBMGS<instance no.> on ECCPRD.

As far as virtual hostname is concerned, you can also HA config without virtual hostname on AIX and for this trick is, when your ASCS will move to other node then when you will start ASCS there it will look for start and instance profile. And in name hostname of primary node will be there. So, you can create copy of profile with hostname of other node. By this way your ASCS will start on both the nodes.

Thanks

Sunny

[Former Member]

Dear Sunny,

Thank you very much for your advice. I believe the procedure you have suggested by copying profiles with different host name is a workaround. Is this the only possible way or is there a proper solution for this for 2 virtual host names.

My confusion is arising by reading the below link:

http://help.sap.com/saphelp_nwpi71/helpdata/en/45/61997b34542a4de10000000a11466f/content.htm

the above link says:

"To be able to install the Central Instance on a different hostname as the database it is important to use the distributed Installation."

Can you please guide me how should I put my requirement in front of the OS team so that they can prepare the servers for me to start SAP HA Installation.

Regards,

Ashish Khanduri

[Former Member]

I suggest you to read the installation guide which has all the required steps documented very well. If you have any doubt then update the thread accrodingly.

- If you want to install CI and DB on different host (without HA) then you need to use Distributed system option to install your SAP.

- If you want to install CI and DB as a part of cluster then you need to use the HA option.

All above requirements are already in installation document.

[Former Member]

Dear Sunny,

I have already read the Installation Guide. I am raising this question here on SDN is only because I have confusion in my mind after reading the Inst Guide & reading the help.sap.com link.

The Inst Guide description of HA installation is listed below. The guide says to install ASCS on host A (ECCPRD). Then it says to install DB Instance on host A (ECCPRD) & then finally CI on host A (ECCPRD). My confusion is that after I have done the installation as mentioned below, then after the installation, when I will move the DB_VG (oracle mount points to host B (ECCDBA) ), then will the oracle start on host B, because it will return the host name as ECCDBA & not ECCPRD (ECCPRD hostname will be registered in oracle control file & listener files).

I hope I am able to make you understand my confusion. Actually what I want is an HA installation with active-active cluster & not distributed installation.

Procedure - SAP Inst Guide:

1.Run SAPinst to install the central services instance (ASCS) using the virtual host name on the primary cluster node, host A.

2.Prepare the standby node, host B. You need to make sure that it meets the hardware and software requirements and it has all the necessary file systems, mount points, and (if required) Network File System (NFS), as described in Performing Switchover Preparations for High Availability [page 64]

3.Set up the user environment on the standby node, host B.

For more information, see Creating Operating System Users [page 51]. Make sure that you use the same user and group IDs as on the primary node. Create the home directories of users and copy all files from the home directory of the primary node.

4.Configure the switchover software and test that switchover functions correctly.

5.Install the database instance on the primary node, host A.

6.Install the central instance with SAPinst [page 77] on the primary node, host A.

NOTE

In a high-availability installation, the central instance does not need to be part of the cluster because it is no longer a single point of failure (SPOF). The SPOF is now in the central services instance (ASCS), which is protected by the cluster.

7.If required, install additional dialog instances with SAPinst [page 77] to replicate the SAP system services that are not a SPOF. These nodes do not need to be part of the cluster.

Regards,

Ashish Khanduri

[Former Member]

First, have you installed the ASCS, CI and DB using physical host name of cluster server or logical server names of cluster group?

[sunny_pahuja2]

Hi,

If you want to install ASCS and DB on different nodes then it is active-active cluster configuration. And you should install it as High Available solution. As far as virtual hostname is concerned, ask them to give u a service hostname which will point to both the nodes. And you should do the installation with service hostname.

Thanks

Sunny

[Former Member]

Dear Sunny,

What you have said is exactly what i have asked our OS team to do.

"As far as virtual hostname is concerned, ask them to give u a service hostname which will point to both the nodes. And you should do the installation with service host name".

But, what the OS team is saying is that one virtual host name can not point to 2 nodes.

Please suggest, how do I make the OS team understand this.

Regards,

Ashish Khanduri

[Former Member]

I think you are getting confused.

Let me clear your doubt.

[Former Member]

Dear Sunil,

I have not started the installation yet. OS team is preparing the servers (OS installation, mount points, cluster , etc.)

Regards,

Ashish Khanduri

[sunny_pahuja2]

Hi Ashish,

You can check below link for virtual hostname configuration:

http://download.oracle.com/docs/cd/B12428_15/install.904/install/ha.htm

Thanks

Sunny

[Former Member]

Hi Ashish,

I think perhaps your trying to achieve the same thing two ways i.e. a distributed SAP install and PowerHA. when maybe you only need to use one of them.

PowerHA does not do really do active-active just as your OS ppl say, you have a service address that at any moment points to node1 OR node2 (never both) . PowerHA has 2 copies of a non distributed install and makes that highly available.

The SAP distributed install is really active-active in that its aware of the fact its on many nodes (powerHA is dumb in that it trys to fool the apps that they are on one host)

Its almost like an MPP cluster vs. HA cluster.

HTH

Chris