Steps to repair oraInventory of Oracle installation

1. Identify Oracle Inventory central location
2. Run the installer as below 

${ORACLE_HOME}/oui/bin/runInstaller -attachHome -invPtrLoc /prj/oracleim/oim/Oracle_IDM1/oraInst.loc  ORACLE_HOME="<ORACLE_HOME>" ORACLE_HOME_NAME="<ORACLE_HOME_NAME>" CLUSTER_NODES="{}"

e.g.,

./runInstaller -attachHome -invPtrLoc /prj/oracleim/oim/Oracle_IDM1/oraInst.loc  ORACLE_HOME="/prj/oracleim/oim/Oracle_IDM1" ORACLE_HOME_NAME="Oracle_Home_Name" CLUSTER_NODES="{}"

An alternative to fix orainventory is to run attachhome command from below location

$ORACLE_HOME/oui/bin/attachHome.sh