High Availability with IBM HACMP after System Installation

[former_member441160]

Hi Friends,

We have to implement High Availability via HACMP of our ECC6 Production

environment; It runs over AIX 5.3.7, with Netweaver 7.0, Oracle 10.2.0.2.

We have installed it some month ago some time ago without the

installation option of Sapinst SAPINST_USE_HOSTNAME to specify virtual

hostname.

We have 2 hosts:

- HOSTA with DB + Central Instance

- HOSTB with Application Server

HOSTB will take over DB + Central Instance if HOSTA fails.

Now, have I to reinstall production system specifying SAPINST_USE_HOSTNAME or could I, adjusting something (ie profiles), have the same as using that option at installation time ?

What SAPINST_USE_HOSTNAME option do ?

Thanks for your help.

Regards.

[former_member441160]

Hi,

coming back to original questions:

1- Now, have I to reinstall production system specifying SAPINST_USE_HOSTNAME or could I, adjusting something (ie profiles), have the same as using that option at installation time ?

2- What SAPINST_USE_HOSTNAME option do ?

I've found the answer in Oss Note 962955:

To ensure that SAP processes use one of these alternative network identities within an SAP instance, you must include the following profile parameters in the start and instance profile of the relevant instance (the installation already does this if you use the SAPinst option SAPINST_USE_HOSTNAME to install the server).

SAPLOCALHOST = <virtual host name>

SAPLOCALHOSTFULL = < full qualified virtual host name>

All SAP processes within the SAP instance that require SAP profiles to start will then use the virtual network identity for future communication.

Thanks a lot to all

[Former Member]

Hi

I would not re-install it for sure.

First of all it would be good to know what type of system you have ABAP only or dual stack system. In all cases you can seperate out the central services which kind of flag an instance to be central. There is a procedure to seperate out ASCS (ABAP central services), however it's not commonly used. Java SCS is normally separated out per default.

From SAP point of view you only need to handle the ASCS and SCS failover.

I would think to do the following changes in the landscape:

1) request network team to create an alias e.g. centralinstance.companyname.com that initially points to normal central instance. This is the kind of virtual hostname

2) Change the message servername and enque server name in the SAP profiles to virtual host and also make sure the SCS instance(es) are starting up with the alias name

3) set up HACMP filesystems (you can do this just as you would do with smitty but you call "smitty hacmp" command)

From DB point of view there are some scenarios:

Data normally should not be on local filesystems. It should be on safe filesystems (e.g. mounted from EMC storage etc...).If this is the case you only need to install an idle DB instance (the software only) to the Application server.

Also you need to create a virtual name which points to the normal DB hostname but in failure it can be redirected to the other instance. There are some SAP parameters and perhaps sidadm environmental variables to point to the right location.

I would also check TNSnames configuration and set it to virtual name in order to let listener pick up requests to the virtual name.

This is only my personal idea as a start and perhaps there will be lot more to do- I recommend to read installation guides and SAP notes.