Miladin Modrakovic's Blog: Oraclue

This is also undocumented feature.As name suggest this utility is used to install patches or to be more precise online patches without shooting down instance ( as you know Oracle  now offers online patching ).

This patch utility can be invoked by running oradebug command:

oradebug patch

Here is list of all available options which are self descriptive:

[list|install|remove|disable|enable]  <file> <temp>
temp = (disabled at restart
default=perm)
file = (in $ORACLE_HOME/hpatch/)

$ORACLE_HOME/hpatch directory contains shared libraries used by online patching.

$ORACLE_HOME/hpatch/orapatch@.cfg ( configuration file )

Oracle has dummy patch 6198642 which can be used to test online patching.You can see it on Laurent’s blog:

http://laurentschneider.com/wordpress/2007/12/oracle-11g-hot-patching.html

and more on online patching:

http://www.oracle.com/technology/deploy/availability/pdf/oracle-openworld-2007/S291525_NowakDutcher.pdf