Oracle DBA Blog: March 2015

taken from :
http://lorenzkeller.blogspot.ae/2015/01/how-to-install-and-manage-java-jdk-on.html

Every Time I set up an Oracle Linux server, I ask myself, how have I done it last time ...

1. Check which Java Version (JDK7, JDK8, ...) is certified with your software.
e.g. Oracle Fusion Middleware supported system configurations:
http://www.oracle.com/technology/software/products/ias/files/fusion_certification.html

2. Check support policy, esp. end of life for your desired Java Version
http://www.oracle.com/technetwork/java/javase/downloads/eol-135779.html

3. Download JDK
http://www.oracle.com/technetwork/java/javase/downloads/index.html

4. Install JDK

# ls -l jdk*
-rw-r--r--. 1 oracle oinstall 126679286 Jan 9 13:01 jdk-7u71-linux-x64.rpm
-rw-r--r--. 1 oracle oinstall 142191827 Jan 9 13:06 jdk-8u25-linux-x64.rpm

# rpm -Uhv jdk-7u71-linux-x64.rpm
Preparing...                ########################################### [100%]
   1:jdk                    ########################################### [100%]
Unpacking JAR files...
    rt.jar...
    jsse.jar...
    charsets.jar...
    tools.jar...
    localedata.jar...
    jfxrt.jar...

5. Check Java Version

# java -version
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)

If this is your expected Java Version - fine! Your are done!
If you still have a pointer to an older version, move on ...

...

6. A non expected Java Version is present?     lets say, JDK8 is still present, but you need to move back to JDK7

# java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

7. Check Java install locations

# ls -l /usr/java/
total 8
lrwxrwxrwx. 1 root root   16 Jan 9 13:24 default -> /usr/java/latest
drwxr-xr-x. 8 root root 4096 Jan 9 13:49 jdk1.7.0_71
drwxr-xr-x. 9 root root 4096 Jan 9 13:40 jdk1.8.0_25
lrwxrwxrwx. 1 root root   21 Jan 9 13:40 latest -> /usr/java/jdk1.8.0_25

8. Make use of alternatives system to switch between versions

8.1 Syntax of alternatives

# /usr/sbin/alternatives
alternatives version 1.3.49.3 - Copyright (C) 2001 Red Hat, Inc.
This may be freely redistributed under the terms of the GNU Public License.

usage: alternatives --install
                    [--initscript ]
                    [--slave ]*
       alternatives --remove
       alternatives --auto
       alternatives --config
       alternatives --display
       alternatives --set

common options: --verbose --test --help --usage --version
                --altdir --admindir

8.2 Register your JDKs for alternatives

usage: alternatives --install

# /usr/sbin/alternatives --install /usr/bin/java java /usr/java/jdk1.7.0_71/bin/java 17071

(where priority represents 17071 for jdk1.7.0_71)

# /usr/sbin/alternatives --install /usr/bin/java java /usr/java/jdk1.8.0_25/bin/java 18025

(where priority represents 18025 for jdk1.8.0_25)

8.3 Now to switch between the versions

8.3.1 Check current java version, again

# java -version
java version "1.8.0_25"
Java(TM) SE Runtime Environment (build 1.8.0_25-b17)
Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

8.3.2 Change the current java version

# /usr/sbin/alternatives --config java

There are 2 programs which provide 'java'.

Selection    Command
-----------------------------------------------
   1           /usr/java/jdk1.7.0_71/bin/java
*+ 2           /usr/java/jdk1.8.0_25/bin/java

Enter to keep the current selection[+], or type selection number: 1

8.3.3 Check your current java version has changed

# java -version
java version "1.7.0_71"
Java(TM) SE Runtime Environment (build 1.7.0_71-b14)
Java HotSpot(TM) 64-Bit Server VM (build 24.71-b01, mixed mode)

9. Keep your path JDK dynamic

The idea is, when you install for example WebLogic Server, to use a dynamic location to your JDK.
I do this with a symbolic link.
I have a folder /opt/oracle/java where I create a symbolic link, that points to the jdk.
As normal user I create the symbolic link:

$ ln -s /usr/java/jdk1.8.0_25 /opt/oracle/java/java

When an updated jdk version in available, after install I only change the symbolic link:

$ rm /opt/oracle/java/java
$ ln -s /usr/java/jdk1.8.0_31 /opt/oracle/java/java

For the WebLogic Server, the path to java will remain. No reconfiguration is needed.
So I only have to restart the WebLogic Server to use the latest JDK.

Oracle DBA Blog

Tuesday, March 31, 2015

How To Install and manage Java JDK on Oracle Linux

Tuesday, March 24, 2015

Setting up Linux with public-yum for all updates