From Oracle FAQ
OPatch is the Oracle database's Interim (one-off) Patch Installer.
If OPatch is not installed into your Oracle Home ($ORACLE_HOME/OPatch), you may need to download it from Metalink and install it yourself.
Syntax and options can be displayed using the -help option:
$ cd $ORACLE_HOME/OPatch $ opatch -help Invoking OPatch 10.2.0.4.2 Oracle Interim Patch Installer version 10.2.0.4.2 Copyright (c) 2007, Oracle Corporation. All rights reserved. Usage: opatch [ -help ] [ -r[eport] ] [ command ] command := apply lsinventory napply nrollback rollback query version prereq util <global_arguments> := -help Displays the help message for the command. -report Print the actions without executing. example: 'opatch -help' 'opatch apply -help' 'opatch lsinventory -help' 'opatch napply -help' 'opatch nrollback -help' 'opatch rollback -help' 'opatch prereq -help' 'opatch util -help' OPatch succeeded.
Listing installed patches
All patches that are installed with Oracle's OPatch Utility can be listed by invoking the opatch command with the lsinventory option. Here is an example:
$ cd $ORACLE_HOME/OPatch $ opatch lsinventory Invoking OPatch 10.2.0.1.0 Oracle interim Patch Installer version 10.2.0.1.0 Copyright (c) 2005, Oracle Corporation. All rights reserved.. ... Installed Top-level Products (1): Oracle Database 10g 10.2.0.1.0 There are 1 products installed in this Oracle Home. There are no Interim patches installed in this Oracle Home. OPatch succeeded.