Opatch: LsInventorySession failed: OracleHomeInventory gets null oracleHomeInfo : OPatch failed with error code 73

{i was trying to opatch lsinventory but it was throwing error as below , i had tried to detach the ORACLE_HOME and attache it again but still i failed
so at last i had removed the oaInventory directory from /oracle/app (after taking a backup of the folder) and did the attach home activity again was successful and opatch lsinventory was also giving correct output}

-- the below was done in non-RAC database env.
-- opatch was throwing the below error

[oracle@subhen-db OPatch]$ ./opatch lsinventory
Invoking OPatch 11.2.0.1.7

Oracle Interim Patch Installer version 11.2.0.1.7
Copyright (c) 2011, Oracle Corporation.  All rights reserved.


Oracle Home       : /oracle/app/database/11.2.0.3/dbhome_2
Central Inventory : /oracle/app/oraInventory
   from           : /etc/oraInst.loc
OPatch version    : 11.2.0.1.7
OUI version       : 11.2.0.3.0
Log file location : /oracle/app/database/11.2.0.3/dbhome_2/cfgtoollogs/opatch/opatch2013-03-15_11-22-00AM.log

List of Homes on this system:

  Home name= OraDb11g_home1, Location= "/oracle/app/database/11.2.0.3/dbhome_2/OPatch"
Inventory load failed... OPatch cannot load inventory for the given Oracle Home.
Possible causes are:
   Oracle Home dir. path does not exist in Central Inventory
   Oracle Home is a symbolic link
   Oracle Home inventory is corrupted
LsInventorySession failed: OracleHomeInventory gets null oracleHomeInfo

OPatch failed with error code 73

-- we were also not able to detach the ORACLE_HOME also

[oracle@subhen-db bin]$ ./runInstaller -silent -attachHome -invPtrLoc /etc/oraInst.loc ORACLE_HOME="/oracle/app/database/11.2.0.3/dbhome_2" ORACLE_HOE_NAME="OraDb11g_home1" "CLUSTER_NODES={}"
Starting Oracle Universal Installer...

Checking swap space: must be greater than 500 MB.   Actual 1278 MB    Passed
The inventory pointer is located at /etc/oraInst.loc
The inventory is located at /oracle/app/oraInventory
OUI-10198:Unable to create a new Oracle Home with name OraDb11g_home1. An Oracle Home with this name already exists. Please select another name.
'AttachHome' failed.

[oracle@subhen-db bin]$ ./runInstaller -silent -detachHome -invPtrLoc /etc/oraInst.loc ORACLE_HOME="/oracle/app/database/11.2.0.3/dbhome_2" ORACLE_HOE_NAME="OraDb11g_home1" "CLUSTER_NODES={}"
Starting Oracle Universal Installer...

Checking swap space: must be greater than 500 MB.   Actual 1278 MB    Passed
The inventory pointer is located at /etc/oraInst.loc
The inventory is located at /oracle/app/oraInventory
'DetachHome' failed.

-- remove/move oraInventory directory in order to recreate it from fresh

[oracle@subhen-db app]$ pwd
/oracle/app
[oracle@subhen-db app]$ mv oraInventory oraInventory.old

[oracle@subhen-db bin]$ ./runInstaller -silent -attachHome ORACLE_HOME="/oracle/app/database/11.2.0.3/dbhome_2" ORACLE_HOME_NAME="OraDb11g_home2"
Starting Oracle Universal Installer...

Checking swap space: must be greater than 500 MB.   Actual 1278 MB    Passed
The inventory pointer is located at /etc/oraInst.loc
The inventory is located at /oracle/app/oraInventory
'AttachHome' was successful.

[oracle@subhen-db OPatch]$ ./opatch lsinventory
Invoking OPatch 11.2.0.1.7

Oracle Interim Patch Installer version 11.2.0.1.7
Copyright (c) 2011, Oracle Corporation.  All rights reserved.


Oracle Home       : /oracle/app/database/11.2.0.3/dbhome_2
Central Inventory : /oracle/app/oraInventory
   from           : /etc/oraInst.loc
OPatch version    : 11.2.0.1.7
OUI version       : 11.2.0.3.0
Log file location : /oracle/app/database/11.2.0.3/dbhome_2/cfgtoollogs/opatch/opatch2013-03-15_14-35-59PM.log

Lsinventory Output file location : /oracle/app/database/11.2.0.3/dbhome_2/cfgtoollogs/opatch/lsinv/lsinventory2013-03-15_14-35-59PM.txt

--------------------------------------------------------------------------------
Installed Top-level Products (1):

Oracle Database 11g                                                  11.2.0.3.0
There are 1 products installed in this Oracle Home.


There are no Interim patches installed in this Oracle Home.


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OPatch succeeded.