Refreshing.....

OraInventory
The first time you install Oracle Database software on a server, you are prompted to specify the location of Inventory directory, called oraInventory. This directory provides a centralized inventory of all Oracle software products installed on the server. You should use the same value for the Oracle inventory directory each time you perform an Oracle software installation on
the server.
Below gud information from Atul's Blog:
What is oraInventory ?oraInventory is repository (directory) which store/records oracle software products & their oracle_homes location on a machine. This Inventory now a days in XML format and called as XML Inventory where as in past it used to be in binary format & called as binary Inventory.There are basically two kind of Inventory Global Inventory (also called as Central Inventory) and Local Inventory also called as Oracle Home Inventory.Global Inventory ?Global Inventory holds information about Oracle Products on a Machine. These products can be various oracle components like database, oracle application server, collaboration suite, soa suite, forms & reports or discoverer server . This global Inventory location will be determined by file oraInst.loc in /etc (on Linux) or /var/opt/oracle (solaris). If you want to see list of oracle products on machine check for file inventory.xml under ContentsXML in oraInventory (Please note if you have multiple global Inventory on machine check all oraInventory directories)You will see entry likeHOME NAME="ORA10g_HOME" LOC="/u01/oracle/10.2.0/db" TYPE="O" IDX="1"/......Local InventoryInventory inside each Oracle Home is called as local Inventory or oracle_home Inventory. This Inventory holds information to that oracle_home only.

Can I have multiple Global Inventory on a machine ?Quite common questions is that can you have multiple global Inventory and answer is YES you can have multiple global Inventory but if your upgrading or applying patch then change Inventory Pointer oraInst.loc to respective location. If you are following single global Inventory and if you wish to uninstall any software then remove it from Global Inventory as well.

What to do if my Global Inventory is corrupted ?No need to worry 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.locORACLE_HOME="Oracle_Home_Location" ORACLE_HOME_NAME="Oracle_Home_Name"CLUSTER_NODES="{}"

Simply...oraInventory is where oracle stores the inventory details of all the patches and components it has installed.

1) oraInventory could be placed anywhere which can be determined from inventory_loc in oraInst.loc. For oratab and oraInst.loc, OUI looks for those files usually at:/var/opt/oracle/oraInst.loc (typical)/etc/oraInst.loc (AIX and Linux)HKEY_LOCAL_MACHINE -> Software -> Oracle -> INST_LOC (Windows platforms)2) Correct. "oraInstRoot.sh" will be created for you by OUI and once you run it successfully you do not need it anymore.3) Please note that there are two inventories with the newer releases of OUI (2.x and higher): - The inventory in the ORACLE_HOME (Local Inventory)- The central inventory directory outside the ORACLE_HOME (Global Inventory)For more details about the two inventories, please check Note: 360079.1 - Global and Local Inventory explained

If this is the first time you are installing any Oracle software on this computer, then the Create Inventory Directory window appears. You must specify a local for the inventory, which OUI uses to keep track of all Oracle software installed on the computer. This information is used while applying patches or upgrading an existing installation, and while deinstalling Oracle software. Note that this directory is different from the Oracle home directory. The recommended value for the inventory directory is Oracle_base/../oraInventory, or one level above the Oracle base directory, in the oraInventory subdirectory. If you Oracle base directory is /u01/app/oracle, then the Oracle inventory directory defaults to /u01/app/oraInventory.