Tuesday, October 7, 2014

SAP Kernel and its types of releases

- Update 11/01/2019 -

SAP Kernel similarly as kernel of operating system is a central module of SAP application server type of ABAP. It is a basis for all programs executed by ABAP AS. It does represent interface between OS that hosts SAP app and SAP app itself. Physically the kernel is represented by process running on OS (file like SAPEXE, SAPEXEDB, disp+work, tp, R3trans, lib_dbsl). SAP AS kernel is loaded first while SAP system is starting up. It provides all essential services (e.g. memory management) required by SAP application components. It is programmed in C/C++ programming language. There are methods in the kernel that are implemented in the kernel of the ABAP runtime environment instead of in an ABAP program.
SAP kernels is always build for particular version of operating system, database and respective compiler.  This needs to be noticed when files of the kernel are being downloaded from SAP Support portal.

What are different types of SAP kernel?

standard kernel:
This is normal SAP kernel built for specific OS/DB/compiler. By naming convention this type of kernel can be recognized as: ABC_REL (where ABC stands for 3-digit abbreviation of version e.g. 720_REL - standard SAP Kernel. which is downward compatible with older versions of OS and database clients. It was compiled on older versions of OS Compilers and linked to older database client libraries.

Extension Kernel (EXT):
By the time when the OS/DB/compiler for a particular platform reaches the end of support, SAP will make a newer kernel with a newer version of the operating system and compiler called the EXT kernel. From naming convention point of view this can be recognized based on following abbreviation: ABC_EXT e.g. 720_EXT - new extended kernel, which is released for recent OS releases and database clients. It does not support older versions of operating system platforms.

Downward Compatible Kernel (DCK):
The SAP kernel versions are usually developed as downward compatible. This means that higher version kernels may not be only used in systems of same version but in systems of lower versions (e.g. kernel of version 4.6D in system of Basis Component 4.6D but also lower versions like 4.6C, 4.6B, etc.). Notice that there must be an SAP Note published to indicate that recent kernel release can be used as downward compatible kernel. In case there is the DCT kernel available patched for older kernel (replaced by DCK one) are not being provided anymore. Kernels are marked as DCK if the kernel can be used to correct errors without you having to a need to upgrade the system.

UC - UniCode enabled kernel

The kernel has to be upgraded from time time to as there might be an security issues popping up here and there. How the kernel can be upgraded? The kernels are normally upgraded just by replacing executable files directly on OS level file system. Old kernel files are replaced by new one. This is purely technical activity that has no impact on business processes implemented in particular SAP system.

More information:
1629598 - SAP Kernel 720 will replace older kernel versions
1553300 - 7.20 EXT Kernel - Extended Kernel Maintenance

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