Rolling Kernel Switch and Linux Server Patch Activity without Business Downtime

[asharma49]

In this article, I am going to explain how to perform Rolling Kernel Switch and Linux server Patch Activity  manually without Business Downtime.
Now days for customers main challenge is near zero downtime and with this objective – I performed SAP Kernel upgrade and Linux kernel patch activity leveraging Linux High Availability and Rolling Kernel switch features .
There was no impact to Business Operation during this major maintenance activity.

First let's understand what is Rolling Kernel Switch feature :

Rolling kernel switch (RKS) feature is to minimize planned downtimes for the switch of the SAP kernel. The RKS procedure is based on the fact that the application servers are given a new kernel version one after the other, rather than at the same time. Since this means that application servers with different kernel versions work together on a temporary basis, you must make sure that the kernel versions in question are compatible with each other. We call this RKS compatibility. 

High Level steps which i preformed to achieve zero downtime for complete Kernel and Linux patch upgrade activity.

Objective : To achieve zero downtime for Kernel upgrade and Linux patch activity - There are 2 maintenance activity .

Environment Details : SAP S/4HANA , 2 Application Servers , ASCS and ERS with Peacemaker cluster setup ,ASCS running on Central Service Server 1 and ERS running on Central Service Server 1

High Level Steps:

Step 1: Download the required or recommended kernel patch from SAP Service Marketplace as usual. Link to download SAP Kernel for both Database Dependent and Database Independent kernel files.

SAP KERNEL 64-BIT UNICODE/  : ( You need to download based upon your target kernel patch ) 

Step 2: Remove Application Server2 from SMLG logon group 

Step 3:  Remove Application Server 2 from Default Job group from Transaction SM61.

Step 4 : Make sure there is no active users and  jobs running on App Server 2 - You can place system message well in advance.

Step 4:  Stop SAP services on  Application Server 2 

Step 5: Move running ASCS/ERS service from Central Service Server 2 to Server 1.

 pcs resource move <ASCS/ERS Resource Group > < Central Service Server 1>   

After running this command - Both ASCS and ERS are running on Central Service Server 1 for temporarily purpose

Step 6: Perform Kernel Upgrade from Application Server 2:

./SAPCAR1 -xfj SAPEXE_<Target Patch>.SAR    ( You need to select kernel files as per your target kernel version and release ) 

./SAPCAR1 -xfj SAPEXEDB_<Target Patch>.SAR ( You need to select kernel files as per your target kernel version and release ) 

./saproot.sh <SID>

Here we are using Global Kernel directory for placing new kernel files so these are getting upgraded for all other application servers automatically after restart.

Step 7: Handover Application Server 2 and Central Services Server 2 to Infrastructure Team for Linux patching

Step 8 : Once Application Server 2 and Central Service Server 2 are back from Infrastructure Team.- Start SAP services on Application Server 2 

Step 9: Add Application Server 2 in SMLG and SM61 - Default Job group and perform validation 

Step 10: Repeat the same step 2 -7 for Application Server 1  ( except step 6 - as new kernel files are already placed in Global kernel directory ) and Handover App Server 1 and Central Service Server 1 to Infrastructure team for Linux Patching

Step 11: Once App Server 1 and Central Service Server 1 are back from Linux team after patching – Start SAP services  , Perform Step 9.

Referred SAP Notes:

• SAP Note: 953653 Rolling Kernel Switch https://launchpad.support.sap.com/#/notes/953653
• SAP Note : 2254173 Linux: Rolling Kernel Switch in Pacemaker-based NetWeaver HA environments https://launchpad.support.sap.com/#/notes/2254173

Hope this article will help you to understand how to perform Rolling Kernel Switch and Linux server patch activity  manually without disturbing Business .

Thanks !!

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