Oracle database fails with ORA-27123: unable to attach to shared memory segment Linux-x86_64 Error:

Hi All,

In my Production database which is of version 11.1.0.7 users are unable to connect to database with the below error. This issue has happened twice.

ORA-27123: unable to attach to shared memory segment

Linux-x86_64 Error: 23: Too many open files in system

While the Open file related settings seems to be fine in the system.

Limits for the user who owns the database installation is

[oraprd@iXXXXXXX TEMP]$ 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) 786496

max locked memory       (kbytes, -l) 50000000

max memory size         (kbytes, -m) unlimited