SAP on IBM i – Update week 47 2014: Performance Considerations when Upgrading to Kernel Release 7.4x
When you are planning an upgrade or update to a higher SAP release, you have always been advised to test carefully and check SAP Notes for potential additional resources that may be required for the new release. For example, SAP Note 1974405 explains that you may need 5 to 10 percent more CPU resources when upgrading to SAP ERP Central Component 6.0 EHP7. However, SAP recently got feedback from customers, that the additional CPU resources may exceed that in some cases. These customers have experienced longer response times after upgrading to a release that contains SAP_BASIS at release 7.40 and a kernel at release 7.40 or higher (for example by upgrading to SAP ERP Central Component 6.0 EHP7).
Compared to release 7.2x, the SAP kernel has undergone major changes in 7.4x, in particular in the area of memory management and process communication. To get the best performance from this kernel, SAP has put together SAP Note 2098347 with a list of recommendations, among them:
- Configure a standalone enqueue server as described in SAP Note 2013043.
- Make sure to have a current patch level, at least 7.41 patch level 47 or 7.42 patch level 14.
- For lib_dbsl in release 7.41 install at least patch level 115, for lib_dbsl in release 7.42 install at least patch level 29 (see SAP Note 2101009).
- Use profile parameter ES/TABLE=SHM_SEGS along with as4/MAXSHR64=2048. Please note that ES/SHM_BASE_ADDR should not longer be set explicitely with kernel release 7.4x (see SAP Note 808607).
- Set profile parameter rdisp/queue/use_events_for_dispatching=on (default in 7.42 patch level 14, see SAP Note 2050408).
- Verify the settings of your memory related profile parameters, because beginning with 7.40 all defaults are calculated based on the physical size of the main storage (parameter PHYS_MEMSIZE, see SAP Note 2085980).
- Verify the buffer settings in transaction ST02, in particular the CUA buffer. With 7.40, the maximum number of entries is no longer calculated from the buffer size but explicitly set through profile parameter rsdb/cua/max_objects (see SAP Notes 702728 and 2044752).
SAP Note 1387644 recommends setting the profile parameter SETENV_xx = LDR_CNTRL=DATAPSIZE=64K@TEXTPSIZE=64K@STACKPSIZE=64K@SHMPSIZE=64K for the operating system AIX. For the operating system IBM i, no significant improvement was noticed as a result of setting this parameter. Therefore, we do not recommend setting this parameter. If you still want to set the parameter, make sure that the PTFs 5770999-MF59805 for IBM i 7.1 or 5770999-MF59810 for IBM i 7.2 are applied.
If additional settings that help the overall performance of the 7.4x kernel are identified, SAP will update SAP Note 2098347. Please always reference the note to get the latest information.