MSCS Cluster - expectations

[Former Member]

Hi, I would like to get your valuable inputs on the below areas.

I have setup an MSCS cluster and have installed SAP application (ABAP+JAVA) on it. I have ERS for ABAP and Java on each node. PAS and AAS, one on each node as well. The message server fails over with no trouble (whenever a failure happens), comes back in less than a minute.

Q1 - When the message server fails over, I am losing my SAPGUI session, What I mean is, if I am logged in to SAPGUI, and have my window open, the session is lost during the failover. Is this normal? if this is not, could you please tell me what could be something I should be looking at?

Q2 - If I were to run a process chain load during the time of failover, what will happen to the process chain? It could be a background job, or a PI interface load.. what would happen to the function?

Can you please provide your valuable inputs from your experience with MSCS?

[Former Member]

Sorry for the late reply. My tests prove that the users will get disconnected when the message server fails over. However, the jobs/message processing will not fail. When moving the ASCS between the nodes, the message clearly says that it will disconnect users. If you have a different experience on the failover, please let me know. This will help me verify my installation is correct or not. Thanks again for all the inputs.

[Sriram2009]

Hi Jim

This is normal operation in the Windows MSCS failover environment. All the end user connection will be disconnected with a minute time users can be connected to another node and do the there operations.

BR

SS

[isaias_freitas]

Hello,

Can you post a screenshot showing the services and resources of the SAP cluster group?

I do not see why you would get disconnected.

I'll perform some tests at a test system I have access to, and will post the results.

Regards,

Isaías

[isaias_freitas]

Hello,

I performed the test, and I did not lost my connection to the SAP GUI.

The test system I used was installed per SAP standards (e.g., only the database and the ASCS are part of the cluster).

Regards,

Isaías

[Former Member]

That suprises me, and few people who commented that the "user connections would be lost".  Also, see the message from MSCS which says that you will lose client connections. I dont have much clarity now.

[isaias_freitas]

If you were performing the failover of the ASCS, the "clients" would be the SAP instances, not the end users.

End users are not connected to the ASCS.

[Sriram2009]

Hi Jim

During the peak time just perform the failover and check the result of client connections ..

BR

SS

[Former Member]

lol..Gettingfired101?

I see that the clients (users in my case) are getting disconnected.

[Former Member]

This reply helped me !

[Sriram2009]

Hi Jim

Q1 - When the message server fails over, I am losing my SAPGUI session, What I mean is, if I am logged in to SAPGUI, and have my window open, the session is lost during the failover. Is this normal? if this is not, could you please tell me what could be something I should be looking at?

Yes, Its normal operations during the failover time those who are active connections will be disconnected. less then a minute time you can reconnection the SAPGUI with second node on MSCS.

Q2 - If I were to run a process chain load during the time of failover, what will happen to the process chain? It could be a background job, or a PI interface load.. what would happen to the function?

Normally if the SAP group on cluster failover to another node all the bg jobs which running on may go failed or cancelled status. once the resources are online you can retry the same process chain BG jobs.

BR

SS

[Former Member]

Thanks S Sriram. From what you said, my cluster is working as expected.

Thanks Manu. Your answer contradicts to Sriram's. My DB is not clustered. My message servers are. All I am trying to understand is - what happens to my SAPGUI session and a running BACKGROUND Job when my node fails over.

Any other inputs? I want to make sure that the action i see is normal.

[isaias_freitas]

Hello,

If only the ASCS is in cluster (as it should be), you should not get disconnected from SAP GUI.

However, if you have added the PAS/AAS to the cluster (not the normal SAP HA setup), you will get disconnected if you failover the PAS/AAS.

The SAP standard HA setup (not including DB here) would be:

ASCS in cluster

PAS/AAS not part of the cluster

-> when cluster node 1 (server itself) fails (e.g., hardware/OS crash, power failure, ...):

---> PAS will go down and any user that was logged on to it will get disconnected;

---> any job running on PAS will fail;

---> cluster will failover ASCS to node 2;

-> everything that was running at node 2 (including SAP GUI users logged on to it) would not be affected in any way;

-> users that were disconnected will be able to logon again after the ASCS is up at node 2.

[manumohandas82]

Sorry ,  Didnt know your DB was not clustered .

You should not get disconnected as your A(SCS ) is in the cluster , [ an already logged in user is already connected to dispatcher and tied to an application server so how does he get disconnected  if the MS goes down and s the lock held by him  is  not deleted]  . In case you have installed additional application server ( As suggested BY Isaias ) in the cluster and you are logged on to that server , yes then you  should get disconnected .

In case you have no  application server installed on the cluster

     No jobs are supposed to fail as you have also an ERS running  .

     Believe you should  check  on the implementation of ERS , in case you get disconnected on certain transactions like SMLG , RZ12 ( where lock is      involved )

Thanks ,

Manu

[manumohandas82]

Hi Jim ,

Not Sure on MSCS , But The HA requires the DB and (A)SCS to be available at all times with no disruption in case of failure .

In an HA environment

Q1 :   . Your sesion should not be interupted , Nor you should loose any locks (in SM12 , if ERS )  in the system

Check whether you have set the following

DB Reconnect Parameters - SAP High Availability - SAP Library

Check the value of rdisp/gui_auto_logout parameter in SAP

Q2 .  No disruption should happen incase of a failover .  [ It all depends on how well you have implemented ERS ]

http://www.arrowecs.cz/web/infobaze.nsf/0/bd972748ed006334c1257640001f10c9/$FILE/HA_for_SAP_on_VMwar... [A comparison with MSCS )

Thanks ,

Manu