Kernel Upgrade - Standard Step-by-Step Guide

SAP Kernel Upgrade:

The SAP Kernel is the core set of executable programs that power an SAP system. Keeping the kernel updated is crucial for maintaining system stability, performance improvements, and security patches.

A successful SAP Kernel upgrade requires careful planning and execution. Below is a structured, step-by-step guide to help you navigate the upgrade process efficiently.

?? Step 1: Check Compatibility

Before upgrading, you need to ensure that the target kernel version is compatible with:

?? Your SAP product version

?? Your operating system (OS) version

?? How to verify? Use the Product Availability Matrix (PAM), available on SAP Support Portal, to check compatibility. Upgrading to an incompatible version could lead to unexpected issues, so this step is critical.

?? Step 2: Download the Required Kernel Files

Once the compatible version is identified, download the necessary files from the SAP Support Portal and place them on your SAP server.

?? The files you need:

Database-independent kernel file → SAPEXE*.SAR

Database-dependent kernel file → SAPEXEDB*.SAR

These files contain the essential executables required to run SAP and are specific to your database.

?? Step 3: Prepare for the Upgrade

Before proceeding, create a dedicated directory to store the new kernel files.

?? Run the following command:

mkdir new_kernel

This directory acts as a temporary workspace to extract and prepare the new kernel before replacing the existing one.

?? Step 4: Copy Kernel Files

Now, copy the downloaded kernel files to the new directory you created.

?? Use this command:

cp -pr SAPEXE*.SAR SAPEXEDB*.SAR /new_kernel

This ensures that you have a separate working copy of the kernel files before extracting them.

?? Step 5: Extract Kernel Files

To extract the kernel files, use the SAPCAR utility, which is SAP's standard tool for handling compressed archives.

?? Run the following commands:

SAPCAR -xvf SAPEXE*.SAR

SAPCAR -xvf SAPEXEDB*.SAR

This will unpack the kernel executables and prepare them for installation.

?? Tip: If SAPCAR is not available on your system, you may need to download the latest version from SAP Support Portal.

?? Step 6: Set Ownership and Permissions

Once the kernel files are extracted, ensure they have the correct ownership and permissions.

?? Set the correct user ownership:

chown -R <sid>adm:sapsys *

?? Grant necessary permissions:

chmod -R 777 *

This step ensures that the SAP instance can access and execute the new kernel files without permission issues.

?? Step 7: Stop Application Services

Before replacing the existing kernel, stop all SAP application services.

?? Verify that no SAP processes are running for the <sid>adm user using:

ps -ef | grep <sid>adm

Stopping services prevents corruption or conflicts during the upgrade.

?? Step 8: Take a Backup of the Existing Kernel

Taking a backup of the current kernel is a best practice in case you need to revert due to unexpected issues.

?? Backup the global directory:

cp -prf linuxx86_64 linuxx86_64_YYYYMMDD # Use date format for easy tracking

?? Check the sizes to confirm a successful backup:

du -sh linuxx86_64

du -sh linuxx86_64_YYYYMMDD

Without a proper backup, rolling back the kernel upgrade will not be possible.

?? Step 9: Copy the New Kernel to the Global Directory

Now that the old kernel is backed up, proceed with copying the new kernel files to the global directory.

?? Use the command:

cp -pr * /sapmnt/<SID>/exe/uc/linuxx86_64

The global directory is where the system looks for the kernel, so updating it ensures all SAP instances use the new kernel.

?? Step 10: Verify the New Kernel Version

After copying, confirm that the new kernel version is installed correctly.

?? Run the following command:

disp+work -version

This should display the updated kernel version, ensuring that the upgrade was applied successfully.

?? Step 11: Execute saproot.sh Script

To apply the necessary ownership and security settings, run the saproot.sh script as the root user.

?? Command:

./saproot.sh <SID>

This script ensures the correct permissions are assigned to key executables like br*, sapuxuserchk, and icmbnd.

?? Step 12: Start the SAP Instance

Once everything is in place, restart the SAP instance.

?? This can be done using:

sapcontrol -nr <instance_number> -function StartSystem ALL

Monitor the logs for any errors during startup.

?? Step 13: Distribute Kernel to Local Directories

SAP automatically synchronizes the kernel from the global directory to the local directories using the sapcpe process.

This ensures that all application servers use the updated kernel.

?? Step 14: Perform Final Validation

After the instance is running, verify the kernel version from the application layer.

?? To check from SAP GUI:

Open SM51 transaction

Select the application server

Click on Release Notes to verify the new kernel version

Once confirmed, your SAP Kernel upgrade is successfully completed! ??

?? Key Takeaways:

? Always check compatibility before upgrading

? Take a full backup of the existing kernel

? Ensure proper file permissions and ownership

? Verify the kernel version after deployment

? Monitor the system post-upgrade for stability