Opatch WLS 12c

Backup Oracle Home:
It is highly recommended that you back up the Oracle home before any patch operation. You can back up the Oracle home using your preferred method. You can use any method such as zip, cp -r, tar, and cpio to compress the Oracle home.

Opatch path:
/Users/German/Oracle/Middleware/Oracle_Home/OPatch

List patches:
./opatch lsinventory
./opatch lsinventory -detail

Check if it's feasible:
./opatch apply /Users/German/tmp/patches/23639929 -report

if the next message appears:

JAVA_HOME is not set or does not exist

then add (jre path) :

-jre /Library/Java/JavaVirtualMachines/jdk1.7.0_201.jdk/Contents/Home

Apply patch:
./opatch apply /Users/German/tmp/patches/23639929

Rollback patch
./opatch rollback -id 23639929

logs:

ORACLE_HOME/cfgtoollogs/opatch/

More info:
https://docs.oracle.com/middleware/1213/core/OPATC/toc.htm

Too many open files

The following problem may occurr in WLS:

Caused By: java.net.SocketException: Too many open files
  at java.net.Socket.createImpl(Socket.java:447)
  at java.net.Socket.connect(Socket.java:577)
  at oracle.net.nt.TcpNTAdapter.connect(TcpNTAdapter.java:161)
  at oracle.net.nt.ConnOption.connect(ConnOption.java:159)
  at oracle.net.nt.ConnStrategy.execute(ConnStrategy.java:428)
  at oracle.net.resolver.AddrResolution.resolveAndExecute(AddrResolution.java:506)
  at oracle.net.ns.NSProtocol.establishConnection(NSProtocol.java:595)
  at oracle.net.ns.NSProtocol.connect(NSProtocol.java:230)

This is a common issue when  File Descriptors are not enough for the OS processes.

Checking the most open FD appear WLS Managed Servers and they are almost on the limit:

4076 376 /u04/Middleware/WLS12c/jdk/bin/java-server-Xms1024m-Xmx2048m-XX:PermSize=256m-XX:MaxPermSize=512m-Dweblogic.Name=WLS02

4063 32526 /u04/Middleware/WLS12c/jdk/bin/java-server-Xms1024m-Xmx2048m-XX:PermSize=256m-XX:MaxPermSize=512m-Dweblogic.Name=WLS01

Checking with lsof -p <pid> we see a lot of open jar files from war files, because we have several war files deployed.

Check:

$ ulimit -n
4096

Therefore the solution is to set a bigger soft & hard limit.