SAP on AIX

SAP kernel 793 on AIX is released for S/4HANA 2023 - see SAP Note 3372947.

Before installing the new kernel, make sure you read SAP Note 1780629 - AIX: Minimal OS Requirements for SAP Kernel and update your system to the AIX level and the C++ runtime level that are required to run this kernel.  On AIX, SAP kernel 793 is built using the IBM Open XL C/C++ for AIX 17.1.1 compiler which supports advanced C++ language features. These features are only supported on POWER8 or newer IBM POWER servers.

SAP kernel 793 on AIX comes with built-in 64K page size support. Especially if you did not use 64K pages with earlier kernel releases, you should see a performance improvement. For more information see SAP Note 3385801.

SAP Kernel 754 is released as downward compatible kernel for older kernels 740 up to 753 (see SAP Note 3156866). On AIX, this kernel was built with a newer compiler which is able to exploit current IBM POWER processor instructions. As a result, you can expect to see performance improvements compared to 753 or earlier kernels in particular when running the kernel on POWER9 or POWER10 servers. Furthermore, kernel 754 on AIX comes with built-in 64K page size support. Especially if you did not use 64K pages with earlier kernel releases, you should see a nice additional performance boost. Please note that in order to switch to 754 kernel you should first update your server to the required AIX and C++ runtime levels. (see SAP Note 1780629). Consider using AIX Live Kernel Update to avoid the downtime that would otherwise be associated with the AIX update.

SAP Note 1780629 - AIX: Minimal OS Requirements for SAP Kernel

Active Memory Expansion (AME) is a feature that allows AIX to utilize more memory than the configured real memory. AME uses hardware-accelerated memory compression to achieve this. In the past, AME only supported 4K memory pages and was also only supported for SAP with 4K page sizes. 64K page size support in AME has been available in AIX since AIX 7.1 and POWER8 servers. Now, this option is also available and supported for SAP. The 64K variant of AME is highly recommended. Tests with SAP workload have shown that it offers significant advantages compared to the 4K variant. For more details see the SAP Note 1464605 which was updated to include 64K page sizes.

When your AIX server runs into low memory or low paging space situations this can lead to an outage of your SAP system. Therefore, you should try hard to avoid these scenarios. SAP Note 1121904 will help you to properly configure both memory and paging space.

Running out of virtual memory on your SAP application server is something you definitely want to avoid. Check out this SAP note which contains valuable hints and tips and best practices how to accomplish this. Learn about the SAP Host Agent metric OS.PercentPSBelowSigdanger which allows you to set an alert before your application server runs into problems.