All FMW products except the WebLogic server is patched via the opatch tool. From FMW 12.1.2 the WebLogic server is also patched by opatch.

In a FMW installation you can have many Oracle Homes. When you install a patch you need to know which home to apply the patch to.

opatch can help you figure out where to install the patch.

I have a Forms installation that I need to apply a patch to.

I can use find to locate the homes that has an opatch installation.

[oracle@wintermute forms112]$ find . -name OPatch -type d | grep -v Templates
./pfrd_binaries/OPatch
./oracle_common/OPatch

But the domain might not use all the installed products.

Instead I can ask opatch which Oracle Homes is used by a domain.

[oracle@wintermute ~]$ cd /u01/app/oracle/product/forms112/oracle_common
[oracle@wintermute oracle_common]$ ./OPatch/opatch lshomes -domain FR112 | grep "Home path"
Home path = "/u01/app/oracle/product/forms112/oracle_common"
Home path = "/u01/app/oracle/product/forms112/pfrd_binaries"

The FR112 domain uses two Oracle Homes.

I have a patch that need to be applied to one of them. I can ask opatch which home the patch can be installed in.

[oracle@wintermute ~]$ cd /u01/app/oracle/product/forms112/oracle_common
[oracle@wintermute oracle_common]$ ./OPatch/opatch checkapplicable -ph /u01/software/forms/p16837591_111210_Generic/16837591 | grep -A 1 "The patch 16837591"
The patch 16837591 can be applied to the following homes (1):
/u01/app/oracle/product/forms112/pfrd_binaries
--
The patch 16837591 cannot be applied to any of following homes.
/u01/app/oracle/product/forms112/oracle_common

You can read more about patching FMW with opatch in “Oracle Fusion Middleware Patching Guide 11g Release 1 (11.1.1.7.0)”