SAP Kernel
Kernel upgrade is a keen and effective process to keep SAP system health in a high.
As part of Basis, we all come across kernel upgrade. I would like to share my experience in a kernel upgrade, process.
In general, what is Kernel?
In computing, the kernel is a computer program that manages I/O (input/output) requests from software, and translates them into data processing instructions for the central processing unit and other electronic components of a computer. The kernel is a fundamental part of a modern computer's operating system.
Now how we relate a kernel to SAP:
Running Applications: All ABAP applications run on software processors (virtual machines) within this component.
User and process administration: This component is responsible for the tasks that usually belong to an operating system.
Database access: Each NetWeaver AS ABAP is linked to a database system, consisting of a database management system (DBMS) and the database itself.
Communication: ABAP applications can communicate both with other SAP Systems and with external systems.
Downloads:
Types of Kernel are available in service market place.
- 32/64 bit Unicode & extended
- 32/64 non Unicode systems & extended
By executing disp+work in a cmd line of OS level we can easily get the kernel version, release, Unicode or non Unicode, real or extended. We need to log as a SIDADM or navigate to existing kernel directory to get this information.
Need to download the exact kernel as per:
- Operating system
- Unicode/Non Unicode
- Real/extended
Kernel files are divided in to 2 parts:
- Kernel Part I (database independent)
- Kernel Part II (database specific)
Before Kernel Upgrade:
In the above example: We need to Upgrade N-1. ( N is the latest version)
SAP kernel 7.21 64 BIT Unicode files / patch 402 Part 1 and Part 2, once we downloaded the file we can extract.
Process:
STOPSAP and stop services – disable SAP services before we implement a new kernel.
Reason behind is few files and executables are responsible to start and run SAP application server and few executables are responsible to write logs or update. If we try to replace SAP kernel on fly it may prompt an error file in use.
We have caused a corruption in the kernel directory; new files might be overwritten already. It’s a severe error that we leave a corrupted kernel directory. Few scenarios we may need to restart SAP or if any cause of system shutdown. SAP may through some errors while starting up back when it has a corrupted kernel directory.
Recommended process to STOP SAP, stop SAP services and disable SAP services in services.msc.
Take a back up of existing kernel directory and keep in a safe place. Just in case if we need to revert back to older kernel
Replace existing kernel directory with a new kernel files.
Kernel directory will be located in
\usr\sap\SID\SYS\exe\uc\NTAMDXX
After implementing new kernel we can start SAP
To verify kernel use same CMD: disp+work
Tricky Part:
After replacing kernel if it’s failed to start SAP service:
- Check the kernel file whether we have downloaded the appropriate one if there is a mismatch in Unicode to non Unicode.
- Replace with old back up file by renaming back to same before; do not try to copy and paste again with kernel directory as of few files might have been overwritten already.
- If we still have error in starting SAP. We can try to replace with dev/Qas/prd kernel in the same landscape for time being.
Wrapping up:
Replacing kernel upgrade is a small effort but it’s important one to keep system up and running in a stabilized manner. Though we get a minimal down time to upgrade kernel, utilize time by preparing it before with guidelines and read kernel upgrade Note first and follow it up for a smoother implementation of new kernel.
Regards,
Rathish Soundrapandian.
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