Linux Summary

1. Set security limits AND kernel parameters as recommended in relevant Oracle Installation Guide
2. Set memory as below (on Linux use cat /proc/meminfo )
3. Set filesystem_io_options as below
4. Set hugepages as below (not with memory_target)

• 11g: Set memory_target=75%ram. = DON’T use hugepages. Set filesystemio_options=setall
• 10g: Set sga_target=32%ram and pga_aggregate_target=32%ram. Use hugepages. Set filesystemio_options=setall
• 10gDW: Set sga_target=25%ram and pga_aggregate_target=50%ram, use hugepages, set filesystemio_options=setall

• Asynchronous I/O Support on OCFS/OCFS2 and Related Settings: filesystemio_options, disk_asynch_io
• HugePages on Linux: What It Is... and What It Is Not...
• Shell Script to Calculate Values Recommended Linux HugePages / HugeTLB Configuration
• HugePages and Oracle Database 11g Automatic Memory Management (AMM) on Linux
• Werner Puschitz, Tuning and Optimizing Red Hat Enterprise Linux for Oracle 9i and 10g Databases
• Oracle Database Installation Guide 11gR2 for Linux

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1) Werner Puschitz’s recommendations for /etc/security/limits.conf are:

oracle           soft    nofile            63536

oracle           hard    nofile            63536

oracle           soft    nproc             16384

oracle           hard    nproc             16384

oracle           soft    memlock         1048576

oracle           hard    memlock         1048576

2) Werner Puschitz: "it is recommended to set SEMOPM equal to SEMMSL." That would mean us increasing SEMOPM from 100 to 250. Do that by editing /etc/sysctl.conf and changing line:

kernel.sem = 250 32000 100 128

to:

kernel.sem = 250 32000 250 128

3) Example - we need 7642 hugepages to hold current server SGAs. Best to give it a little bit more headroom for future databases / increases to existing sgas – maybe to the same size as the current shmmax of 8gb? Make the change with, e.g.:

echo "vm.nr_hugepages=8192" >> /etc/sysctl.conf

4) From Metalink Note 401749.1, Shell Script to Calculate Values Recommended HugePages / HugeTLB Configuration:

#!/bin/bash
#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
#
# Note: This script does calculation for all shared memory
# segments available when the script is run, no matter it
# is an Oracle RDBMS shared memory segment or not.

# Check for the kernel version
KERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`

# Find out the HugePage size
HPG_SZ=`grep Hugepagesize /proc/meminfo | awk {'print $2'}`

# Start from 1 pages to be on the safe side and guarantee 1 free HugePage
NUM_PG=1

# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | awk {'print $5'} | grep "[0-9][0-9]*"`
do
   MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q`
   if [ $MIN_PG -gt 0 ]; then
      NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q`
   fi
done

# Finish with results
case $KERN in
   '2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`;
          echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;;
   '2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    *) echo "Unrecognized kernel version $KERN. Exiting." ;;
esac

# End