As you know, SAP is continuously improving their products by providing new releases of their software in all its different components, among them, as one of the most important components, the kernel for SAP NetWeaver ABAP. While providing new releases to implement new functionality, SAP has to maintain compatibility to products that have been in the market for quite a while. To resolve this conflict, SAP has introduced the concept of a downward-compatible kernel, i.e. a kernel that is created for a newer ABAP release but can still be used with older ABAP releases.
A similar challenge exists related to the operating system. While SAP would like to use enhanced features of new operating system releases, they also have to support older operating system releases for backward compatibility, especially when using a downward-compatible kernel. When support for an SAP product lasts for very many years, the original operating system releases and compilers may no longer be supported by the vendor (in this case, IBM), so SAP produces so-called EXT-Kernels, that start at a higher minimum operating system release, but are running in today’s supported environments.
Currently SAP supports two lines of downward-compatible kernels: 7.2x (7.20, 7.20 EXT, 7.21 and 7.21 EXT) for SAP NetWeaver releases 7.00, 7.01, 7.02, 7.03, 7.10, 7.11, 7.20, 7.30 and 7,31, and 7.4x (7.40, 7.41 and 7.42) for SAP NetWeaver release 7.40. The support of the different kernels in the available IBM i operating system releases is documented in SAP Note 68440 and shown in the following picture:
Please note that certain SAP NetWeaver releases may require a higher minimum operating system release than the underlying kernel. The required minimum operating system release level for a specific SAP product or SAP NetWeaver release can be found in the Product Availability Matrix at https://service.sap.com/sap/support/pam.
As you can see, the kernel releases 7.20 and 7.21 are supported down to IBM i V5R3M0, which is no longer in maintenance at IBM since end of April 2009. However, SAP has recently discovered that some incompatible changes were introduced with kernel release 7.20, patch level 434 and kernel release 7.21, patch level 124, so that kernels at this or a higher patch level require a minimum release of IBM i V5R4M0. If you are still running at IBM i V5R3M0, you must stay below those patch levels or upgrade to a higher operating system release (recommended!). SAP is planning to undo these changes, but the corrections will not become available before the next stack-kernels (SAPEXE and SAPEXEDB), which are planned to be shipped in the first quarter of 2015.
SAP will end support for kernel release 7.20 in the first quarter of 2015 (see SAP Note 1744209). Around that time frame, a new kernel release will be shipped for the 7.2x line (most likely named release 7.22). SAP is planning to require a minimum operating system level of IBM i V5R4M0 for this kernel release, even though it is downward-compatible to SAP NetWeaver 7.00, which was first released for IBM i V5R3M0.