Lets say that you want to apply some patch:
Starting Oracle Universal Installer...
Checking installer requirements...
Checking operating system version: must be redhat-3, SuSE-9, SuSE-10, SuSE-11, redhat-4, redhat-5, UnitedLinux-1.0, asianux-1, asianux-2 or asianux-3
All installer requirements met.
Preparing to launch Oracle Universal Installer from /tmp/OraInstall2011-11-18_12-09-55PM. Please wait ...
And after launching runInstaller you wait forever for the Oracle Universal Installer and it never shows, and in an eureka moment you decide to check the java distributed with the patch:
oracle@myserver$ java -version
java version "1.4.2"
gcj (GCC) 3.4.6 20060404 (Red Hat 3.4.6-9)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
oracle@myserver$ /tmp/OraInstall2011-11-18_12-09-55PM/jre/1.4.2/bin/java -version
As documented in Metalink note 391844.1, there is a bug in the JDK version bundled with the installer so you need to install another java distribution. Metalink note 400227.1 lists different methods according to your Oracle version and operating system so for example, in case of installing Oracle patch 10.2.0.4 in a Linux Itanium server, you have to download patch 5390722 and after installing it, you can launch OUI more or less this way:
./runInstaller -jreLoc $ORACLE_HOME/jre
Oracle 10g R2 Installation Problem