SGeSAP Supported configuration

[Animesh Chakraborty]

Hi All MCSG Expert,

We are going to implement a ServiceGuard on SAP system .The configuration is shown in the attached ppt. It's going to be
a 3 nodes cluster; 1st node is SAP dbci, 2nd node running sap application pkg.
the 3rd one will be alternate node running devlopement instance, and QAS
instance.
Now My question is is it supported configuration by HP ?

Some thoughts:
For failover, the Alternate node is the failover node for both the DB/CI pkg and the App server pkg.

1.Scenario one: App server fails, and later DB/CI server fails. If the App server node fails, while DB/CI node is fine, will SGeSAP provide a way to allow the App pkg to fail over to the Alternate Node? Or will this be done separately? I could not tell if it is allowed to have regular SG pkg failover controls in a SGeSAP cluster. If it is ok, then the App pkg failover could trigger the Test/Dev system to shutdown. Later, if the DB/CI node would to fail, SGeSAP should be able to fail over the DB/CI pkg to the Alternate Node where the App pkg is running. Pls confirm.

2.Scenario Two: DB/CI server fails, and later App server fails. I understand that SGeSAP can fail over the DB/CI pkg to the Alternate node that was running Test/Dev. (This is the long green arrow in the Failover operation diagram on the right hand side).

3.Scenario Two: DB/CI server fails, and later App server fails. I understand that SGeSAP can fail over the DB/CI pkg to the Alternate node that was running Test/Dev. (This is the long green arrow in the Failover operation diagram on the right hand side).

4.Continuing on Scenario Two... The short green arrow in the Failover operation diagram shows that the App pkg could fail over to the Alternate Node, while DB/CI is running there. I don't see this (App --> DB/CI failover) as a supported scenario in the SGeSAP Switchover Scenarios (slide 10), so can this be done?

5.In this configuration, it is possilbe that DB/CI may be failing over to a node that is either running the App pkg or the Test/Dev system. Does this create any complexity to the SGeSAP set up?

6.) What other thoughts do you have?

Thanks in advance for your help for your time.


Regards
Animesh

[Dietmar Konermann]

Hi, Animesh!

Some short notes concerning your questions...

First of all, be advised to use SGeSAP 3.08 with its patch PHSS_29090 if you plan to use AS packages. Also take care to have a look at the latest documentation, which is the June 2003 release of "Managing SGeSAP", http://docs.hp.com/hpux/pdf/B7885-90018.pdf.

Concerning your questions:

1) There are two ways to configure AS packages. Either they are controlled completely by SG (1) or they are controlled completely by SGeSAP (2). If you want AS packages to failover automatically, you need to use option (1). Then the AS package is not automatically halted/started with DBCI. Also does the AS package not check if a DBCI is already there where it start.

2) No question.

3) Same as 2).

4) If you use the option (1) above, then AS can failover to the DBCI system... but does this make sense? Are DBCI and AS configured "so small" that they can run on the same node? Why don't you simply configure DBCI to load the system 100%...

5) The DBCI package can be easily configured to halt any other AS package during failover. No addtl. complexity from my point of view.

6) In general AS instances are not considered as Single Points of Failure, since you can configure lots of them for redundancy. Thus SGeSAP is not really designed to protect such AS instances with failover capabilities. Furthermore the AS package is a flexible possibility to load otherwise idle failover systems.

So in summary SGeSAP does not provide, what you plan to do. However, it should be easy to use option(1) and add some things like:

- let AS package check if DBCI is already there
- let AS package halt test instances on failover

I would be your task to test and support these additions, IMHO. :-)

Best regards...
Dietmar.

[Animesh Chakraborty]

Hi Dietmer,
I have a got reply from your Germany office(Markus) as below:

"Application Server packages can be treated as full Serviceguard packages with SGeSAP 03.09.
SGeSAP 03.09 is planned to be available with AR0903 in September.
So all statements are applicable to SGeSAP 03.09 only."

Thanks
Animesh

[Dietmar Konermann]

OK, Markus Ertl should know about the future SGeSAP roadmap. :) I wasn't sure if this enhancement has been officially committed, so I didn't speculate about 3.09. Thanks for your feedback.