low open file descriptor limit

[Steve Reynolds]

We recently upgraded to Oracle 9i.
When the database is started the following
message appears.

Oracle instance running on a system with low open file descriptor limit. Tune your system to increase this limit to avoid severe performance degradation.

What kernel parameter, if any, should I look at
adjusting?. Is it possibly on the Oracle end?

[Pete Randall]

Sounds like nfile to me!


Pete

[Patrick Wallek]

I suspect they are talking about the 'nfile' kernel parameter.

nfile - set maximum number of files that can be open simultaneously on the system at any given time

Tunable kernel parameters documentation:
http://docs.hp.com/hpux/onlinedocs/TKP-90202/TKP-90202.html

[RAC_1]

The parameter you are looking for is nfile. This is the limit on system wide open files.

Anil

[Pete Randall]

Though it could possibly be maxfiles or maxfiles_lim, I still think nfile.


Pete

[Muthukumar_5]

We can control open file descriptor's based on nfile kernel parameter there.

Try to check as,

kmtune -l -q nfile

IF you are 11.23 then use kctune there.

And also see maxfile,maxfile_lim parameter's too.

You can go to sam to make changes there too. Reboot is needed after configuring them.

[Steve Reynolds]

Thanks for the replies, I appreciate it.

I have checked nfile with sar -v 5 5

file-sz
2411/65546 0
2412/65546 0
2411/65546 0
2411/65546 0
2411/65546 0

Unless the Oracle start-up is using tens of
thousands of processess, I think I am okay on
nfile.

[Kim_18]

There are Oracle 9i release notes for hp-ux which contain minimum kernel parameters for running 9i on hp-ux. May want to check the Oracle Doc. There minimal recommendation for nfile is (15*NPROC+2048.

[Bill Hassell]

65,000 when you're only using 2400 is way too high, assuming your sar measurement was taken when the system was fully loaded. If you typically use 2400 files, I'd make nfile 4000 or 5000. But the limitation you are seeing may be due to the maxfiles kernel parameter, 60 by default. You don't have to change maxfiles to test it though. This parameter limits each program as to the number of files it can open at the same time.

[Steve Reynolds]

The system currently has very little activity. Eventually it will replace a production server.

The current production server stats for sar -v 5 5
This is a low activity for the production server.

file-sz ov
20164/65546 0
20160/65546 0
20411/65546 0
20227/65546 0
20143/65546 0

[Bill Hassell]

I mentioned that you don't have to change the kernel parameter to test whether this is the limit. ulimit (POSIX shell or patched ksh) can change this limit for all processes that start from this shell environment. ulimit -a reports on the current value for maxfiles, ulimit -n 1000 will change the number of files per process to 1000.

Since the current nfile value is so large, maxfiles is probably the limiting value. Now if a process *really* needs several thousand files open at the same time, you can change maxfile_lim which is a hard limit for maxfiles (which is changeable by the program using setrlimit or by the shell). In 11.11, this is a dynamic parameter which means that it can be changed without a reboot.