Problem:

WARNING: Limit of open file descriptors is found to be 1024.

The OMS has been started but it may run out of descriptors under heavy usage.

For proper functioning of OMS, please set "ulimit -n" to be at least 4096.

 

Example:

$ emctl start oms

Oracle Enterprise Manager Cloud Control 12c Release 12.1.0.1.0

Copyright (c) 1996, 2012 Oracle Corporation.  All rights reserved.

Starting WebTier...

WebTier Successfully Started

Starting Oracle Management Server...

Oracle Management Server Successfully Started

Oracle Management Server is Up

WARNING: Limit of open file descriptors is found to be 1024.

The OMS has been started but it may run out of descriptors under heavy usage.

For proper functioning of OMS, please set "ulimit -n" to be at least 4096.

Reason:

Ulimit nofile parameter defines the maximum number of files that can be open by OS user. According to Enterprise Manager Installation guide, “Ensure that you set the soft limit of file descriptor to a minimum of 4096 and hard limit less then or equal to 16384.” which is mention in installation guide:

http://docs.oracle.com/cd/E24628_01/install.121/e22624/install_em_exist_db.htm#BGBHFCAB

Steps to fix that:

1. Check ulimit for nofile soft

$ ulimit -Sn

   1024

2.  Stop the OMS

$ <OMS_HOME>/bin/emctl stop oms -all

3.  Make sure there is no process running from the OMS ORACLE_HOME, kill if any:

$ ps -ef | grep EMGC_ADMINSERVER                                                                                            
$ ps -ef | grep EMGC_OMS1
$ ps -ef | grep java

$ kill -9 <PID>

4.  Increase the ulimit value to 4096. Update ulimit soft to 4096 in file /etc/security/limits.conf as root user

$ vi /etc/security/limits.conf

<UID> soft nofile 4096

5.  Start the OMS

$ <OMS_HOME>/bin/emctl start oms