Memory Management simplifications in ABAP Kernel 7.4*

Memory Management simplifications in ABAP Kernel 7.4*

TABLE OF CONTENTS OVERVIEW. 3 NEW PARAMETER FORMULAS 3 TROUBLESHOOTING.. 4 512 GB LIMIT. 5 CONCLUSION 5 2

OVERVIEW This paper describes Memory Management parameterization changes in 7.4* kernel. The main goal of these changes was simplification: the administrator will be enabled by setting only one profile parameter PHYS_MEMSIZE to automatically initiate changes of dependent parameters. This is a fast way to scale the ABAP instance memory consumption. Within the context of this development the old fashioned Zero Admin MM for Linux and Windows - was extended to all other operating systems and - reimplemented via formula based parameters More information about the Zero Administration in previous releases can be found in: http://help.sap.com/saphelp_erp60_sp/helpdata/en/3c/05863c6800924fe10000000a114084/content.htm http://help.sap.com/saphelp_erp60_sp/helpdata/en/84/7ed384d81f11d188be0000e83539c3/content.htm NEW PARAMETER FORMULAS The formulas may depend on kernel release and operating system. You can get a list of parameters with formula based default values e.g. with help of sappfpar executable. Below is an example for kernel 7.41 PL22 on Linux: > sappfpar all grep "SAP: (" abap/buffersize = (ceil($(em/initial_size_mb)*1024*0.15/4096) * 4096) abap/heap_area_total = (max($(phys_memsize)*1024*1024 * 0.1, $(abap/heap_area_dia) * 2 )) abap/programs = ($(abap/buffersize)/4) abap/shared_objects_size_mb = (min(20000, $(em/initial_size_mb)*0.02)) em/blocksize_kb = (ceil($(em/initial_size_mb) * 1024 / 100000 / 4096) * 4096) em/global_area_mb = (min($(em/initial_size_mb) * 0.05, 32000)) em/initial_size_mb = (min(512000, $(PHYS_MEMSIZE) * 0.7)) em/max_size_mb = ($(em/initial_size_mb)) rdisp/pg_shm = (max(min(1000+40*max(5,floor(($(phys_memsize)-128)*25/128)),16384),1024)) rdisp/max_websocket_connections = ( $(rdisp/tm_max_no) / 2 ) rdisp/wp_ca_blk_no = ($(rdisp/elem_per_queue)*3) rsdb/ntab/entrycount = ($(zcsa/db_max_buftab)) rsdb/ntab/ftabsize = (min(500000, ($(rsdb/ntab/entrycount)))) rsdb/ntab/irbdsize = ($(rsdb/ntab/ftabsize) * 0.2) rsdb/ntab/sntabsize = ($(rsdb/ntab/ftabsize) * 0.1) rsdb/obj/buffersize = (max(4096,$(phys_memsize)*1024 * 0.01)) rsdb/obj/max_objects = (max(2000,$(rsdb/obj/buffersize) / 4)) rsts/ccc/cache07 = ($(rsts/ccc/cachesize) * 0.1) rtbb/buffer_length = ($(zcsa/table_buffer_area) * 0.1 / 1024) rtbb/max_tables = ($(zcsa/db_max_buftab) * 0.1) zcsa/db_max_buftab = (max(20000,$(zcsa/table_buffer_area) / (5 * 1024) )) zcsa/table_buffer_area = (min(3333333333, (max(30000000,($(em/initial_size_mb) * 1024 * 1024 * 0.1))))) ES/SHM_MAX_SHARED_SEGS = ( ($(em/global_area_mb) + $(abap/shared_objects_size_mb) + $(rtbb/buffer_length)/1024 + $(zcsa/table_buffer_area)/1024/1024 ) / $(ES/SHM_SEG_SIZE) + 1 ) Formulas support in the profiles is implemented as of kernel 7.40, described in: http://help.sap.com/saphelp_nw74/helpdata/en/a7/d631e255594dc19899706a3a7c3fe8/content.htm?frames et=/en/51/319798cc7a428a896af0bc2a00adc7/frameset.htm 3

sappfpar can also be used for checking your profile: >sappfpar pf=<profilename> check_formula ***WARNING: formula parameter: abap/buffersize = 350000 found in profile Errors detected: 0 Warnings detected.: 1 In the example above the parameter abap/buffersize that has been set to a fix value although its default value is a formula, was found. TROUBLESHOOTING In this section we would like to analyze a real life example from an administrator s point of view. A system consisting of 2 ABAP instances is installed on a host with 64GB main memory. Every instance is running with PHYS_MEMSIZE=30% setting in profile. Customers experience sporadic memory lack issues - Rabaxes - EmAlloc failed errors in dev trace - Extended Memory Dump in dev trace Examples for memory lack Rabaxes are: TSV_TNEW_PAGE_ALLOC, LOAD_NO_ROLL, STRING_LENGTH_TOO_LARGE, TSV_TNEW_BLOCKS_NO_ROLL_MEMORY The administrator is analyzing Extended Memory Dumps in dev traces, they appear as shown below: Extended Memory Dump Act. USER SUM IM0 IM1 SAP_SMDMON(T52_U5144_M0) [ 0.9] > 0.8< ------ 0990FUSRABCD(T461_U4228_M0) [ 23.8] > 23.6< ------ USER_TEST_12(T461_U4228_M0) [ 23.8] > 23.6< ------ # CHAIN OWNER STATE 0 0 ***free*** free 1 1 EG_GLOBAL_AREA shared 2537 1 EG_GLOBAL_AREA shared 2538 2538 SAP_SMDMON(T6_U377_M0) detached 2539 2539 K8NZDJEQHUR(T558_U15419_M0) detached The administrator can t identify any particular user which is using too much memory. This means that the server has been overloaded sporadically, i.e. at peak times when many users are working simultaneously. 4

Proposed solution: set PHYS_MEMSIZE=45% in the profile to allow every instance to use 64GB * 0.45 = 28,8GB main memory. This will automatically increase the value of dependent parameters, e.g: PHYS_MEMSIZE=30% PHYS_MEMSIZE=45% em/initial_size_mb 13653 (MB) 20480 (MB) abap/heap_area_total 20452265165 (Byte) 30678397747 (Byte) Keep in mind that the instance has to be restarted for activating its new values! PHYS_MEMSIZE can be also set to absolute values instead of percentage: PHYS_MEMSIZE=40000 which would mean Megabytes in the Example above. 512 GB LIMIT FOR ALL OPERATING SYSTEMS PHYS_MEMSIZE is not a hard limit for an ABAP instance. This is a guide value to make the instance aware about the amount of main memory it should use. This limit can be overrunned in heavy load scenarios. Kernel 7.4* has been tested up to PHYS_MEMSIZE=512000 settings. It is not recommended to run a singular ABAP instance with more than 512000 MB. Warnings in dev traces would give you a hint if you are trying to run an instance with more than that memory size, e.g.: * WARNING=>DpCheckParams: invalid value for PHYS_MEMSIZE=600000 [dpinit.c] * WARNING=>DpCheckParams: check message: Parameter value out of range (16512000) [dpinit.c] It is recommended to use default memory management models on every OS: es/implementation = std (Unix) es/implementation = view (Windows) ES/TABLE = UNIX_STD (Unix) ES/TABLE = SHM_SEGS (AIX only) The memory management parameter formulas have been optimized for the memory model cases above. The only platform has been optimized not for default case only is OS/400 which has been tuned for both UNIX_STD and SHM_SEGS memory models. CONCLUSION Formula based parameters introduced in 7.4* and supported for all operating systems offer a new simplified way of administration for ABAP instances in an SAP system. They will be used in ABAP server memory management already. About the author: Gennady Maly is working at SAP development since 2001. 5

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