Database startup fails with ORA-27302: failure occurred at: sskgpsemsper

Error Description
Whenever I try to start my database it fails with ORA-27302: failure occurred at: sskgpsemsper as following.
RMAN> STARTUP FORCE NOMOUNT PFILE='/backup03/webkey/testinitdb.ora';

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of startup command at 09/23/2008 00:45:51
RMAN-04014: startup failed: ORA-27154: post/wait create failed
ORA-27300: OS system dependent operation:semget failed with status: 28
ORA-27301: OS failure message: No space left on device
ORA-27302: failure occurred at: sskgpsemsper

Cause of the problem
The error may mislead you. Though it indicates No space left on device but whenever I issue df -h on my OS there is enough space. The problem happened because of short of semaphores setting in the OS.

Solution of the problem
Solution 1)
Increase number of semaphores on operating system. You set semmns 32767 .
To make the setting permanent make an entry in /etc/sysctl.conf file on linux system.
sem = semmsl semmns semopm semmni
kernel.sem = 256 32768 100 228

Solution 2)
Change the initialization parameter processes to a lower one in the initialization file and then startup the database. In my initialization file processes was set to 555. Whenever I start my database it fails with above error. I then reduced it to by 55 and it started my database successfully.
CREATE PFILE='1.pfile' FROM SPFILE;
edit pfile and set Processes parameter to lower value
STARTUP PFILE='1.pfile';