In this post, I am going to try to explain How you can Remove or Deinstall 11.2.0.1 Grid Infrastructure from your server.

I have 11.2.0.1 grid Infrastructure with 11.2.0.1 database on the AIX 6.1 operating system.

Here are my steps:

1. Verify your Grid Home

[oracle@helios]</> echo $GRID_HOME
/oracle11g/grid/TEST/11.2.0/deinstall

2. Verify your existing diskgroup on ASM

ASM Diskgroups : +ORADATA,+ORAFRA

3. Go to Grid home and follow the below steps:

[oracle@helios]</oracle11g/grid/TEST/11.2.0/deinstall> ./deinstall
Checking for required files and bootstrapping ...
Please wait ...
Location of logs /oracle11g/oraInventory/logs/
############ ORACLE DEINSTALL & DECONFIG TOOL START ############

######################## CHECK OPERATION START ########################
Install check configuration START

Checking for existence of the Oracle home location /oracle11g/grid/TEST/11.2.0
Oracle Home type selected for de-install is: SIHA
Oracle Base selected for de-install is: /oracle11g/db
Checking for existence of central inventory location /oracle11g/oraInventory
Checking for existence of the Oracle Grid Infrastructure home /oracle11g/grid/TEST/11.2.0
Install check configuration END
Traces log file: /oracle11g/oraInventory/logs//crsdc.log
Network Configuration check config START
Network de-configuration trace file location: /oracle11g/oraInventory/logs/netdc_check4275624877467629693.log
Network Configuration check config END
Asm Check Configuration START
ASM de-configuration trace file location: /oracle11g/oraInventory/logs/asmcadc_check8399246761665588773.log
Automatic Storage Management (ASM) instance is detected in this Oracle home /oracle11g/grid/TEST/11.2.0.
ASM Diagnostic Destination : /oracle11g/db
ASM Diskgroups : +ORADATA,+ORAFRA
Diskgroups will be dropped
De-configuring ASM will drop all the diskgroups and it's contents at cleanup time. This will affect all of the databases and ACFS that use this ASM instance(s).
 If you want to retain the existing diskgroups or if any of the information detected is incorrect, you can modify by entering 'y'. Do you want to modify above information (y|n) [n]: y
Specify the ASM Diagnostic Destination [/oracle11g/db]:
Specify the diskgroups that are managed by this ASM instance [+ORADATA,+ORAFRA]:
De-configuring ASM will drop all the diskgroups at cleanup time. Do you want deconfig tool to drop the diskgroups y|n [y]: y

######################### CHECK OPERATION END #########################

####################### CHECK OPERATION SUMMARY #######################
Oracle Grid Infrastructure Home is: /oracle11g/grid/TEST/11.2.0
The cluster node(s) on which the Oracle home exists are: (Please input nodes seperated by ",", eg: node1,node2,...)null
Oracle Home selected for de-install is: /oracle11g/grid/TEST/11.2.0
Inventory Location where the Oracle home registered is: /oracle11g/oraInventory
ASM instance will be de-configured from this Oracle home
Do you want to continue (y - yes, n - no)? [n]: y
A log of this session will be written to: '/oracle11g/oraInventory/logs/deinstall_deconfig2012-02-17_10-38-10-AM.out'
Any error messages from this session will be written to: '/oracle11g/oraInventory/logs/deinstall_deconfig2012-02-17_10-38-10-AM.err'
######################## CLEAN OPERATION START ########################
ASM de-configuration trace file location: /oracle11g/oraInventory/logs/asmcadc_clean5232636268796596481.log
ASM Clean Configuration START
ASM deletion in progress. This operation may take few minutes.
ASM Clean Configuration END
Network Configuration clean config START
Network de-configuration trace file location: /oracle11g/oraInventory/logs/netdc_clean8170400382928543053.log
De-configuring backup files...
Backup files de-configured successfully.
The network configuration has been cleaned up successfully.
Network Configuration clean config END

---------------------------------------->
Run the following command as the root user or the administrator on node "helios".
/tmp/deinstall2012-02-17_10-37-40-AM/perl/bin/perl -I/tmp/deinstall2012-02-17_10-37-40-AM/perl/lib -I/tmp/deinstall2012-02-17_10-37-40-AM/crs/install /tmp/deinstall2012-02-17_10-37-40-AM/crs/install/roothas.pl -force -delete -paramfile /tmp/deinstall2012-02-17_10-37-40-AM/response/deinstall_Ora11g_gridinfrahome1.rsp
Press Enter after you finish running the above commands
<----------------------------------------
Oracle Universal Installer clean START
Detach Oracle home '/oracle11g/grid/TEST/11.2.0' from the central inventory on the local node : Done
Delete directory '/oracle11g/grid/TEST/11.2.0' on the local node : Done
The Oracle Base directory '/oracle11g/db' will not be removed on local node. The directory is in use by Oracle Home '/oracle11g/db/TEST/11.2.0'.
Oracle Universal Installer cleanup was successful.
Oracle Universal Installer clean END

Oracle install clean START
Clean install operation removing temporary directory '/tmp//install' on node 'helios'
Oracle install clean END
Moved default properties file /tmp/deinstall2012-02-17_10-37-40-AM/response/deinstall_Ora11g_gridinfrahome1.rsp as /tmp/deinstall2012-02-17_10-37-40-AM/response/deinstall_Ora11g_gridinfrahome1.rsp1
######################### CLEAN OPERATION END #########################

####################### CLEAN OPERATION SUMMARY #######################
ASM instance was de-configured successfully from the Oracle home
Oracle Restart was already stopped and de-configured on node "helios"
Oracle Restart is stopped and de-configured successfully.
Successfully detached Oracle home '/oracle11g/grid/TEST/11.2.0' from the central inventory on the local node.
Successfully deleted directory '/oracle11g/grid/TEST/11.2.0' on the local node.
Oracle Universal Installer cleanup was successful.
Oracle install successfully cleaned up the temporary directories.
#######################################################################

############# ORACLE DEINSTALL & DECONFIG TOOL END #############

Referance:

How to Deconfigure/Reconfigure or Deinstall Grid Infrastructure [ID 1377349.1]
How to Deinstall Oracle Clusterware Home Manually [ID 1364419.1]