I ran into a situation recently in one of our 11i environments where the Global oraInventory was missing. A missing oraInventory can cause issues when applying patches, so I wanted to correct the issue proactively. Luckily the Local oraInventory was still intact. Looking on Metalink I found Note: 295185.1 which describes how you can recreate the Global oraInventory. The note talks about downloading a patch, but more than likely you already have OUI 2.2, so you probably won't need it.
The steps are pretty simple:
1. Source your Applications environment file.
2. Change to your $IAS_ORACLE_HOME/appsoui/setup directory.
3. Execute the perl script "perl OUIsetup.pl"