How to deinstall 11gR2 Grid Infrastructure and 11gR2 RAC software after upgraded to 12c

SITUATION

We have two nodes 11gR2 GI and RAC upgraded to 12c already, so we need uninstall old both 11gR2 GI and RAC Oracle Home.

SOLUTION

1)Backup OraInventory.

2)Uninstall 11gR2 Oracle RAC Home as below, OraInventory is updated on all nodes accordingly.

$export ORACLE_HOME=/u01/app/oracle/product/11.2.0/db_1
$cd cd $ORACLE_HOME/deinstall
$./deinstall -silent
$cd /u01/app/oracle/product
$rm -r 11.2.0
$cat   inventory.xml|grep 11.2.0
   <saved_with>11.2.0.2.0</saved_with>
<home loc='/u01/app/grid/11.2.0' name='Ora11g_gridinfrahome1' idx='1' type='O'>
<home crs='true' loc='/u01/app/grid/12.1.0' name='Ora12c_gridinfrahome2' idx='15' type='O'>
<home loc='/u01/app/oracle/product/12.1.0/db_1' name='OraDb12c_home1' idx='16' type='O'>
<home /='' removed='T' loc='/u01/app/oracle/product/11.2.0/db_1' name='OraDb11g_home1' idx='2' type='O'>

3) Uninstall 11gR2 Grid Home.

To deinstall 11gR2 GI OH, you will need to use :Oracle Universal Installer (OUI) FAQ( Doc ID 458893.1 ) How to detach an Oracle Home using OUI?  Then after detaching the old GI home then you will need to remove the old GI home manually. Using the information in this note: How to Deinstall Old Clusterware Home Once Upgrade to Newer Version is Complete ( Doc ID 1346305.1 )

$ export ORACLE_HOME=/u01/app/grid/11.2.0
$ $ORACLE_HOME/OPatch/opatch lsinventory -all

$cd $ORACLE_HOME/oui/bin
$ ./runInstaller -silent -detachHome ORACLE_HOME="/u01/app/grid/11.2.0" ORACLE_HOME_NAME="Ora11g_gridinfrahome1"

$ cat   inventory.xml|grep 11.2.0
   <saved_with>11.2.0.2.0</saved_with>
<home crs='true' loc='/u01/app/grid/12.1.0' name='Ora12c_gridinfrahome2' idx='15' type='O'>
<home loc='/u01/app/oracle/product/12.1.0/db_1' name='OraDb12c_home1' idx='16' type='O'>
<home /='' removed='T' loc='/u01/app/oracle/product/11.2.0/db_1' name='OraDb11g_home1' idx='2' type='O'>
<home /='' removed='T' loc='/u01/app/grid/11.2.0' name='Ora11g_gridinfrahome1' idx='1' type='O'>

$ORACLE_HOME/OPatch/opatch lsinventory -all

$ crsctl status res -t

$sudo su -
# cd /u01/app/grid/
# rm -fr 11.2.0