lost your oraInventory ? or somehow corrupted it ?

tricky situation: planned to apply a patch to an oracle home and opatch failes with:

OPatch failed to locate Central Inventory.
Possible causes are: 
    The Central Inventory is corrupted
    The oraInst.loc file specified is not valid.
LsInventorySession failed: OPatch failed to locate Central Inventory.
Possible causes are: 
    The Central Inventory is corrupted
    The oraInst.loc file specified is not valid.

obviously the first thing to check is if the pointer ( oraInst.loc ) points to the correct location and the inventory group is listed correctly:

cat /etc/oraInst.loc 
inventory_loc=/opt/oracle/oraInventory
inst_group=oinstall

this is what it should look like assuming oinstall is really the inventory group and your inventory location is really /opt/oracle/oraInventory. so this part is fine but somehow the oraInventory got lost:

ls -la /opt/oracle/
total 312
drwxrwx--- 4 grid   oinstall   4096 Sep 19 21:54 .
drwxr-xr-x 4 root   root       4096 Mar 23 08:52 ..
drwxrwx--- 4 grid   oinstall   4096 Mar 23 08:43 product
drwxrwx--- 3 grid   oinstall   4096 May  3 23:52 stage

what to do ? restore it from backup would be one solution ( you do regular backups of your inventory, don’t you ? ). let’s assume no backup is available. you still may restore the inventory using the oracle installer available in the oracle home you want to register:

ls -la $ORACLE_HOME/oui
total 60
drwxr-xr-x  8 oracle oinstall 4096 Mar 26 14:23 .
drwxrwx--- 76 oracle oinstall 4096 May  3 23:17 ..
-rwxr-xr-x  1 oracle oinstall  323 Feb 17  2007 admin_langs.xml
drwxr-xr-x  3 oracle oinstall 4096 Mar 26 14:23 bin
-rw-r-----  1 oracle oinstall 6680 Mar 26 14:20 clusterparam.ini
drwxr-xr-x  2 oracle oinstall 4096 Mar 26 14:20 instImages
drwxr-xr-x  4 oracle oinstall 4096 Mar 26 14:20 jlib
drwxr-xr-x  3 oracle oinstall 4096 Mar 26 14:23 lib
-rwxr-xr-x  1 oracle oinstall 2110 Feb 17  2007 nlsrtlmap.xml
-rw-r-----  1 oracle oinstall 6782 Mar 26 14:20 oraparam.ini
drwxr-xr-x  3 oracle oinstall 4096 Mar 26 14:16 prov
-rwxr-xr-x  1 oracle oinstall  748 Feb 17  2007 runtime_langs.xml
drwxr-xr-x  2 oracle oinstall 4096 Mar 26 14:20 schema

even if the inventory is completely lost for recreating it a simple call to the oracle installer will recreate it and register the ORACLE_HOME:

$ORACLE_HOME/oui/bin/runInstaller -silent -attachHome ORACLE_HOME=$ORACLE_HOME ORACLE_HOME_NAME=H11203

if successful you should see the following output:

Starting Oracle Universal Installer...
Checking swap space: must be greater than 500 MB.   Actual 2000 MB    Passed
The inventory pointer is located at /etc/oraInst.loc
The inventory is located at /opt/oracle/oraInventory
'AttachHome' was successful.

… and opatch will succeed from now on.