Most Oracle database installations on Linux require configuration of shell limits. A typical configuration requires the following changes
Add the following lines to /etc/security/limits.conf
oracle soft nproc 2047 oracle hard nproc 16384 oracle soft nofile 1024 oracle hard nofile 65536
Additional memlock limits are required if large pages are configured. The values of these limits is dependent on the number of huge pages allocated. One also occasionally sees other limits such as the stack limit increased.
Add the following line to /etc/pam.d/login
session required pam_limits.so
Add the following lines to /etc/profile
if [ $USER = "oracle" ]; then
if [ $SHELL = "/bin/ksh" ]; then
ulimit -u 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
fi
I normally reboot the system after configuring the above settings.
During an Enterprise Manager Grid Control installation this week, we made the above changes. But when we tried to login to Oracle we hit the following error:
login as: oracle oracle@vm7's password: Last login: Wed Jan 19 05:39:00 2011 from 192.168.5.100 -bash: ulimit: open files: cannot modify limit: Operation not permitted
This error did not occurred if we logged in as root and then entered
[root@vm7]# su - oracle
After some investigation the cause of this error was identified. In /etc/ssh/sshd_config there is a parameter called UsePAM which enables PAM authentication. If this parameter is not set then it defaults to "no". I think it is normally overridden during installation. In order to allow user limits to be set the value should be "yes"
UsePAM=yes
The sshd service must be restarted for the parameter change to take effect:
[root@vm7]# service sshd restart
If the change is successful the new shell limits should be reported by the ulimit command. For example:
[oracle@vm7]$ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 26560 max locked memory (kbytes, -l) 1148576 max memory size (kbytes, -m) unlimited open files (-n) 65536 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes (-u) 16384 virtual memory (kbytes, -v) unlimited file locks (-x) unlimited
In the above example the limits of interest are open files (-n) which should be 65536 and max user processes (-u) which should be 16384.
In many documents (including some Oracle 11gR2 installation guides) the following lines are recommended for /etc/profile
if [ $USER = "oracle" ]; then
if [ $SHELL = "/bin/ksh" ]; then
ulimit -p 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
fi
Not many sites use the Korn shell with Linux but if you do the following error will occur during login:
login as: oracle oracle@vm7's password: Last login: Wed Oct 13 07:25:04 2010 from 192.168.5.100 /etc/profile[58]: ulimit: pipe: is read only
The error occurs because the ulimit -p parameter specifies the number of 512-byte blocks for pipe buffering. The Korn shell man page (man ksh) lists most ulimit parameters, but omits the one we need which is -u to specify the number of processes. So /etc/profile should contain:
if [ $USER = "oracle" ]; then
if [ $SHELL = "/bin/ksh" ]; then
ulimit -u 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
fi
In the Korn shell we can confirm this using ulimit -a
[oracle@vm7]$ ulimit -a address space limit (kbytes) (-M) unlimited core file size (blocks) (-c) 0 cpu time (seconds) (-t) unlimited data size (kbytes) (-d) unlimited file size (blocks) (-f) unlimited locks (-L) unlimited locked address space (kbytes) (-l) 1148576 nofile (-n) 65536 nproc (-u) 16384 pipe buffer size (bytes) (-p) 4096 resident set size (kbytes) (-m) unlimited socket buffer size (bytes) (-b) 4096 stack size (kbytes) (-s) 10240 threads (-T) not supported process size (kbytes) (-v) unlimited
In the above example nofile (-n) should be 65536 and nproc (-u) should be 16384