Initial_size_MB

Question

memlimits output
Posted: Apr 21, 2006 8:46 PM    Reply 
Hi,
When i give memlimits command from the sidadm id, i am getting the following output:
SAP R/3 address space configuration test tool V3.2 (98/01/14)
=========================================================================
Restart, set early swap allocation (PSALLOC=early)
SAP R/3 address space configuration test tool V3.2 (98/01/14)
=========================================================================
Check the maximum data size per process (malloc)
Check the available swap space (malloc in several processes)
Process 1859680 allocating ... Size = 4096MB Total: 4096MB
Upper size limit 4096 reached. Finish checking
Total available swap space = 4096MBCheck the maximum size of mapped file (mmap anonymous,dev/zero)
Check protection operations on this area (protect)
Trying to mmap 512MB ... successfull
Trying to mmap 768MB ... successfull
Trying to mmap 1024MB ... successfull
Trying to mmap 1280MB ... successfull
Trying to mmap 1536MB ... successfull
Trying to mmap 1792MB ... successfull
Trying to mmap 2048MB ... successfull
Trying to mmap 2304MB ... successfull
Trying to mmap 2560MB ... successfull
Trying to mmap 2816MB ... successfull
Trying to mmap 3072MB ... successfull
Trying to mmap 3328MB ... successfull
Trying to mmap 3584MB ... successfull
Trying to mmap 3840MB ... successfull
Trying to mmap 4096MB ... successfull
Upper size limit 4096 reached. Finish checking
Trying to mprotect 4096MB ... successfull
Maximum mapped file size: 4096MB
Maximum mprotect size: 4096MB
R/3 parameter em/initial_size_MB up to 4096 permitted
Check the maximum address space per process usable
both by process local memory and mapped file
Maximum address space ( mmap(4096 MB)+ malloc(1676MB) ): 5772MB
Result
Maximum heap size per process........: 4096 MB
measurement limited to 4096 MB
this value is probably limited by swap space
Maximum mapped file size (mmap)......: 4096 MB
measurement limited to 4096 MB
Maximum protectable size (mprotect)..: 4096 MB
measurement limited to 4096 MB
em/initial_size_MB > 4096 MB will not work
Maximum address space per process....: 5772 MB
Total available swap space...........: 4096 MB
measurement limited to 4096 MB
main memory size x 3 recommended , minimum 1 GB
Check the ones in bold, the swap space in our system is 20GB, the inital size_MB value is 8192 and the blocksize_kb is also 8192. Still the message seems to be like that, what is reason behind this ?
Ours is AIX 64bit and NW04 (R/3 is ECC 5.0)
Thanks

Answer 1

Hi Aravind S,
Note #332591 (memlimits output irritating) contains related information about memlimits and extended memory. The file dev_disp and ST02 transaction are better indications of the amount of memory being allocated to extended memory.
If as recommended according to note #789477 (Lots of Extended Memory on AIX (64-Bit) as of Kernel 6.20) the parameter ES/TABLE = SHM_SEGS, then em/initial_size_MB is not used to set the total extended memory of that instance but instead EM/TOTAL_SIZE_MB.
Notes #835474 (More than 32GB extended memory) and the note #835474 for older releases contain some more related information about relationship between em/blocksize_KB and em/initial_size_MB (or EM/TOTAL_SIZE_MB).
I hope this helps, after setting parameters according to notes above and #146289 (Parameter Recommendations for 64-Bit SAP Kernel), then you can ignore this return from memlimits.
Regards, Mark