ulimit: open files: cannot modify limit: Operation not permitte

在从root用户切换到oracle用户时，碰到了ulimit: open files: cannot modify limit: Operation not permitte的提示信息。字面意思来看即是打开文件受到了限制。同一服务器上，如仅有一个Oracle单实例且数据文件较少的情形应该不会出现该情形。多实例可能会碰到这个情况。由于多个实例都为Oracle用户所有，因此Oracle用户可操作的文件数为所有实例文件数的总和，超出了限制就收到错误提示。

1、故障描述
--在从root切换到oracle时，出现提示
oracle@v2013db02u:/u02/database> su - oracle
Password:
-bash: ulimit: open files: cannot modify limit: Operation not permitted
-bash: ulimit: open files: cannot modify limit: Operation not permitted

a、查看limits.conf配值文件
oracle@v2013db02u:~> more /etc/security/limits.conf
# /etc/security/limits.conf
#
#Each line describes a limit for a user in the form:
#
#<domain>        <type> <item> <value>
#
#Where:
#<domain> can be:
#        - an user name
#        - a group name, with @group syntax
#        - the wildcard *, for default entry
#        - the wildcard %, can be also used with %group syntax,
#                 for maxlogin limit
#
#<type> can have the two values:
#        - "soft" for enforcing the soft limits
#        - "hard" for enforcing hard limits
#
#<item> can be one of the following:
#        - core - limits the core file size (KB)
#        - data - max data size (KB)
#        - fsize - maximum filesize (KB)
#        - memlock - max locked-in-memory address space (KB)
#        - nofile - max number of open files
#        - rss - max resident set size (KB)
#        - stack - max stack size (KB)
#        - cpu - max CPU time (MIN)
#        - nproc - max number of processes
#        - as - address space limit
#        - maxlogins - max number of logins for this user
#        - maxsyslogins - max number of logins on the system
#        - priority - the priority to run user process with
#        - locks - max number of file locks the user can hold
#        - sigpending - max number of pending signals
#        - msgqueue - max memory used by POSIX message queues (bytes)
#        - nice - max nice priority allowed to raise to
#        - rtprio - max realtime priority
#
#<domain>      <type> <item>         <value>
#

#*               soft    core            0
#*               hard    rss             10000
#@student        hard    nproc           20
#@faculty        soft    nproc           20
#@faculty        hard    nproc           50
#ftp             hard    nproc           0
#@student        -       maxlogins       4

# End of file

--limits.conf文件的注释信息给出了很好的描述信息，也即是我们可以基于用户或者组来配置soft及hare方面不同的item
--soft即是软限制，hard是硬限制。用户可以超过soft设置的值，但一定不能超过hard 的值。一般soft比hard小
--上面的这个文件中并未为Oracle用户配值任何信息，且通配符*也被注释了
--由于该服务器为一个新的UAT服务器，Oracle software为Infra安装并配置。从上可知，应该是Infra忘记或忽略了配值该文件
--在数据库实例较少且打开的文件数不多的情形则没有任何问题，随着上面运行的实例增大，现象随之出现

--下面查看一下当前用户的资源分配限制
--对于资源限制，也可以使用ulimit 指令，用来限制用户的资源分配，比如打开文件数，最多进程数，CPU的使用时间
--可以使用指令ulimit -a来查看当前用户的各项limit限制(ulimit用法: man ulimit)

b、查看当前用户的资源限制
oracle@v2013db02u:~> ulimit -a
core file size          (blocks, -c) 0
data seg size           (kbytes, -d) unlimited
file size               (blocks, -f) unlimited
pending signals                 (-i) 540672
max locked memory       (kbytes, -l) 32
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024        -->这里限制了打开的文件数为1024，明显不够
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 16384
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

2、解决办法
a、直接修改limits.conf配值文件，且使得永久生效
--修改文件/etc/security/limits.conf，添加
v2013db02u:~ # echo "
> oracle soft nproc 16384
> oracle hard nproc 16384
> oracle soft nofile 65536
> oracle hard nofile 65536
> oracle soft memlock 4000000
> oracle hard memlock 4000000
> " >> /etc/security/limits.conf

v2013db02u:~ # tail /etc/security/limits.conf

# End of file
oracle soft nproc 16384
oracle hard nproc 16384
oracle soft nofile 65536
oracle hard nofile 65536
oracle soft memlock 4000000
oracle hard memlock 4000000

补充：综合编程 , 其他综合 ,