opatch and Oracle Home inventory

There are two inventory locations. One is the central inventory defined by file /etc/oraInst.loc (in Linux host). For each ORACLE HOME on the server, there is a local inventory at $ORACLE_HOME/inventory.

opatch lists the information first when applying a patch:

Oracle Home                : /path/to/apps/tech_st/10.1.2
Oracle Home Inventory  : $ORACLE_HOME/inventory
Central Inventory           : /path/to/oraEbsInventory
   from                          : /etc/oraInst.loc

Because the central inventory /path/to/oraEbsInventory may be shared by multiple ORACLE HOMEs on the server, it is more vulnerable to error or corruption. If opatch throws out some error, troubleshoot central inventory first.

If there is a problem with local inventory, it may turn out you have to re-install it. So, do not try to change anything without backing it up.

When I apply a small patch to 10.1.2 ORACLE HOME, it failed with below messages in log file $ORACLE_HOME/.patch_storage/8551790/xxx.log. "opatch lsinventory" also did not show the patch was applied.

Patch 8551790 has been applied successfully
... ... ...

verifying patch
  verifying that patch ID is in the Oracle Home inventory
INVENTORY PROBLEM: Patch 8551790 is not present in Oracle Home inventory.
  Verifying copy files.
Comparing "/path/to/8551790/files/procbuilder/lib/cus_procbuilder.mk" and "$ORACLE_HOME/procbuilder/lib/cus_procbuilder.mk"
... ... ...
OPATCH_JAVA_ERROR: Patch was not successfully applied.

Verification of the patch failed.
ERROR: OPatch failed as verification of the patch failed.

The real message is "INVENTORY PROBLEM ...".  Doc ID 438067.1 (Updating the Inventory Is Failing During Patching) provides a solution to it.

Fix:
I renamed the existing Contents folder and created an empty folder Contents under oraEbsInventory. After I ran "opatch apply" again, the issue was fixed.

The same fix may address error "Inventory check failed: Patch ID is NOT registered in Oracle Home inventory." or "Verification of patch failed: Patch is not found in the Inventory." as well.

That Oracle document also says "opatch lsinventory -detail" accesses the inventory stored in text format in central inventory while "opatch lsinventory" gets inventory info from binary inventory (under oraEbsInventory/Contents ?).