Difference between Local Inventory and Global Inventory in oracle

oraInventory:
The Orainventory is the location for the OUI's Book keeping the inventory stores information about.

*) All the Oracle software products installed on all ORACLE_HOMES on a machine
*) Other non-oracle products such as Java Runtime env's (JRE)


Global Inventory:
Global Inventory holds the information about Oracle Products on a Instance, The inventory contains the high level list of all oracle products installed on a machine such as ORACLE_HOMES or JRE.

There should be only one per machine. Its locations is defined in the oraInst.loc in /etc (on Linux) or /var/opt/oracle (solaris).

Local Inventory:
Inventory inside each Oracle Home is called as local Inventory or ORACLE_HOME Inventory. This Inventory holds information to that ORACLE_HOME only.

What to do if my Global Inventory is corrupted?
If your global Inventory is corrupted, you can recreate global Inventory on machine using Universal Installer and attach already Installed oracle home by option

-attachHome

./runInstaller -silent -attachHome -invPtrLoc $location_to_oraInst.loc ORACLE_HOME=Oracle_Home_Location ORACLE_HOME_NAME=Oracle_Home_Name CLUSTER_NODES={}