Unable to create Patch Object error applying 12.1.0.2 Oct Patch

$opatch prereq CheckConflictAgainstOHWith
Oracle Interim Patch Installer version 12.2.0.1.8
Copyright (c) 2017, Oracle Corporation.  All rights reserved.

PREREQ session

Oracle Home       : /u01/app/oracle/product/12.1.0.2/db_1
Central Inventory : /u01/app/oraInventory
   from           : /u01/app/oracle/product/12.1.0.2/db_1/oraInst.loc
OPatch version    : 12.2.0.1.8
OUI version       : 12.1.0.2.0
Log file location : /u01/app/oracle/product/12.1.0.2/db_1/cfgtoollogs/opatch/opatch2017-02-07_23-31-04PM_1.log

Invoking prereq "checkconflictagainstohwithdetail"

Prereq "checkConflictAgainstOHWithDetail" is not executed.

The details are:
Unable to create Patch Object.
Exception occured : PatchObject constructor: Input file "/u01/app/oracle/product/12.1.0.2/db_1/OPatch/auto/etc/config/actions" or "/u01/app/oracle/product/12.1.0.2/db_1/OPatch/auto/etc/config/inventory" does not exist.

OPatch failed with error code 2



To Resolve the issue:

Finding the issue:

Unable to create Patch Object.
Exception occured : PatchObject constructor: Input file
"/u01/app/oracle/product/12.1.0.2/db_1/OPatch/auto/etc/config/actions"
or "/u01/app/oracle/product/12.1.0.2/db_1/OPatch/auto/etc/config/inventory" does not exist.

Note : Opatch is looking for a inventory directory is in wrong location  due to that the issue occurred. Change the correct directory and execute the patch again.

Solution:

We changed the working directory to patch location then issue got fixed.

Chech the Patch Conflict Again:
--------------------------------------
$ opatch prereq CheckConflictAgainstOHWithD
Oracle Interim Patch Installer version 12.2.0.1.8
Copyright (c) 2017, Oracle Corporation.  All rights reserved.

PREREQ session

Oracle Home       : /u01/app/oracle/product/12.1.0.2/db_1
Central Inventory : /u01/app/oraInventory
   from           : /u01/app/oracle/product/12.1.0.2/db_1/oraInst.loc
OPatch version    : 12.2.0.1.8
OUI version       : 12.1.0.2.0
Log file location : /u01/app/oracle/product/12.1.0.2/db_1/cfgtoollogs/opatch/opatch2017-02-07_23-36-37PM_1.log

Invoking prereq "checkconflictagainstohwithdetail"

Prereq "checkConflictAgainstOHWithDetail" passed.

OPatch succeeded.