LINUX
« Previous EntriesLinux : Adding a Directory to the Path
Wednesday, November 4th, 2009The best place to add a directory to the path of a single user is to modify that user’s .bash_profile file.
To add it to all users except user root, add it to /etc/profile.
To also add it to the path of user root, add it to root’s .bash_profile file.
vi editing mode quick reference
Friday, October 30th, 2009Shortcut Description
Switching to COMMAND Mode:
ESC Switch to command mode.
Commands for Entering INPUT Mode:
i Insert before cursor.
a Insert after cursor.
I Insert at the beginning of line.
A [...]
Linux Oracle tuning parameter : Shutdown GUI
Friday, June 5th, 2009Modify the ‘inittab’ file to set boot level as 3:
Linux Oracle tuning parameter : Disable Unnecessary Daemons
Friday, June 5th, 2009/sbin/chkconfig –levels 2345 sendmail off
/sbin/chkconfig sendmail off
Linux Oracle tuning parameter : Tune TCP
Friday, June 5th, 2009To view current TCP settings, run command:
sysctl net.ipv4.tcp_keepalive_time
net.ipv4.tcp_keepalive_time = 7200 // 2 hours
where net.ipv4.tcp_keepalive_time is a TCP tuning parameter.
To set a TCP parameter to a value, run command:
sysctl -w net.ipv4.tcp_keepalive_time=1800
Linux vs. Oracle Tuning, Error : ORA-00845: MEMORY_TARGET not supported on this system
Friday, June 5th, 2009The ORA-00845:can arises for the following two reasons on linux system.
1)If the shared memory which is mapped to /dev/shm directory is less than the size of MEMORY_TARGET or MEMORY_MAX_TARGET.
or,
2)If the shared memory is not mapped to /dev/shm directory.
Make sure /dev/shm is properly mounted. You can see it by,
df -h
Filesystem [...]
Linux Oracle tuning parameter : Message queues
Friday, June 5th, 2009To view current settings, run command:
more /proc/sys/kernel/msgmni
more /proc/sys/kernel/msgmax
To set it to a new value for this running session, which takes effect immediately, run command:
echo 2048 > /proc/sys/kernel/msgmni
echo 64000 > /proc/sys/kernel/msgmax
Linux Oracle tuning parameter : shmmax and shmall
Friday, June 5th, 2009maximum amount of memory = shmall * pagesize
where pagesize = getconf PAGE_SIZE and shmall = cat /proc/sys/kernel/shmall
Linux Oracle tuning parameter : Semaphores
Friday, June 5th, 2009To view current settings, run command:
more /proc/sys/kernel/sem
250 32000 32 1024
To set it to a new value for this running session, which takes effect immediately, run command:
echo 500 512000 64 2048 > /proc/sys/kernel/sem
Parameters meaning:
SEMMSL – semaphores per ID
SEMMNS – (SEMMNI*SEMMSL) max semaphores in system
SEMOPM – max operations per semop call
SEMMNI – max semaphore identifiers
Linux Oracle tuning parameter : Shared Memory
Friday, June 5th, 2009To view current settings, run command:
more /proc/sys/kernel/shmmax
To set it to a new value for this running session, which takes effect immediately, run command:
echo 268435456 > /proc/sys/kernel/shmmax
To set it to a new value permanently (so it survives reboots), modify the sysctl.conf file:
…
kernel.shmmax = 268435456