Kernel Tuning

SAP R/3 systems need a lot of resources. We therefore added the following parameters to the kernel configuration file:

# Set these for memory pigs (SAP and Oracle):
options MAXDSIZ="(1024*1024*1024)"
options DFLDSIZ="(1024*1024*1024)"
# System V options needed.
options SYSVSHM #SYSV-style shared memory
options SHMMAXPGS=262144 #max amount of shared mem. pages
#options SHMMAXPGS=393216 #use this for the 46C inst.parameters
options SHMMNI=256 #max number of shared memory ident if.
options SHMSEG=100 #max shared mem.segs per process
options SYSVMSG #SYSV-style message queues
options MSGSEG=32767 #max num. of mes.segments in system
options MSGSSZ=32 #size of msg-seg. MUST be power of 2
options MSGMNB=65535 #max char. per message queue
options MSGTQL=2046 #max amount of msgs in system
options SYSVSEM #SYSV-style semaphores
options SEMMNU=256 #number of semaphore UNDO structures
options SEMMNS=1024 #number of semaphores in system
options SEMMNI=520 #number of semaphore identifiers
options SEMUME=100 #number of UNDO keys

The minimum values are specified in the documentation that comes from SAP. As there is no description for Linux, see the HP-UX section (32-bit) for further information. As the system for the 4.6C SR2 installation has more main memory, the shared segments can be larger both for SAP and Oracle, therefore choose a larger number of shared memory pages.

Note: With the default installation of FreeBSD on i386™, leave MAXDSIZ and DFLDSIZ at 1 GB maximum. Otherwise, strange errors like “ORA-27102: out of memory” and “Linux Error: 12: Cannot allocate memory” might

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