Create or attach the central inventory in Oracle Database

1. Find the existing location of Central inventory.

Windows
1. By default Central Inventory location in windows is at “C:\Program Files\Oracle\Inventory”.
2. If you don’t find then you will check the “inst_loc” key in Window registry:
Go to Regedit in research --> Open Registry editor --> HKEY_LOCAL_MACHINE/SOFTWARE/ORACLE --> Find "inst_loc".
3. Find in 64-bit command prompt as follows:
reg query HKLM\SOFTWARE\ORACLE /v inst_loc
4. Find in 32-bit with command prompt:
reg query HKLM\SOFTWARE\WOW6432Node\ORACLE /v inst_loc

Unix or Linux
1. Default Central inventory location present in the file /etc/oraInst.loc (AIX and Linux) or /var/opt/oracle/oraInst.loc (other platform)
2. If you don’t find then you can create the file with oraInst.loc please take care of capital or small letters Linux is case sensitivity.
Example:
inventory_loc=/u01/oracle/oraInventory
inst_group=oinstall

2. If already exists then rename the old inventory and if not exists then create the default location as mentioned in above step.

3. Go to the OUI directory in your command prompt or command shell as follows:

-- Windows:
cd %ORACLE_HOME%\oui\bin

--Linux or Unix:
cd $ORACLE_HOME/oui/bin


4. Attach the home or create the home with runInstaller script as follows:

-- Windows:
setup.exe -silent -ignoreSysPrereqs -attachHome ORACLE_HOME="" ORACLE_HOME_NAME=""

--linux:
./runInstaller -silent -ignoreSysPrereqs -attachHome ORACLE_HOME="" ORACLE_HOME_NAME=""


5. For Example you need to set Oracle_home and Oracle_home_name as value to attached the Oracle Home with new inventory or existing inventory:

./runInstaller -silent -ignoreSysPrereqs -attachHome ORACLE_HOME="/u01/oracle/product/12.1.0" ORACLE_HOME_NAME="OraDb12c_home1"

Note: If you have more than one home then execute last step by changing oracle_home and oracle_home_name parameter