Uninstall oracle
Often,we install oracle database and database software in day to day life.But have you ever completely cleanup the old debris and software from your machine frequently? In oracle we call it as deinstall the software
Here i show a basic deinstall steps to gracefully wipe out all the database files and temporary files

Delete the database using dbca

choose existing database to delete

Confirm to delete the database



After database deletion deconfig the high availability service forcefully using the perl script in grid home
[root@exdbadm01 apps01]# /apps01/base/product/11.2.0/grid/crs/install/roothas.pl -deconfig -force
Using configuration parameter file: /apps01/base/product/11.2.0/grid/crs/install/crsconfig_params
CRS resources for listeners are still configured
PRKO-2573 : ONS daemon is already stopped.
CRS-2673: Attempting to stop 'ora.DATA.dg' on 'exdbadm01'
CRS-2673: Attempting to stop 'ora.FRA.dg' on 'exdbadm01'
CRS-2677: Stop of 'ora.FRA.dg' on 'exdbadm01' succeeded
CRS-2677: Stop of 'ora.DATA.dg' on 'exdbadm01' succeeded
CRS-2673: Attempting to stop 'ora.asm' on 'exdbadm01'
CRS-2677: Stop of 'ora.asm' on 'exdbadm01' succeeded
CRS-2673: Attempting to stop 'ora.cssd' on 'exdbadm01'
CRS-2677: Stop of 'ora.cssd' on 'exdbadm01' succeeded
CRS-2791: Starting shutdown of Oracle High Availability Services-managed resources on 'exdbadm01'
CRS-2673: Attempting to stop 'ora.diskmon' on 'exdbadm01'
CRS-2677: Stop of 'ora.diskmon' on 'exdbadm01' succeeded
CRS-2673: Attempting to stop 'ora.evmd' on 'exdbadm01'
CRS-2677: Stop of 'ora.evmd' on 'exdbadm01' succeeded
CRS-2793: Shutdown of Oracle High Availability Services-managed resources on 'exdbadm01' has completed
CRS-4133: Oracle High Availability Services has been stopped.
Successfully deconfigured Oracle Restart stack
Deinstall the grid software from grid home
[oracle@exdbadm01 dbhome_1]$ pwd
/data01/base/product/11.2.0/dbhome_1
[oracle@exdbadm01 dbhome_1]$ cd deinstall/
[oracle@exdbadm01 deinstall]$ ./deinstall
Checking for required files and bootstrapping ...
Please wait ...
Location of logs /data01/orainventory/logs/
############ ORACLE DEINSTALL & DECONFIG TOOL START ############
######################### CHECK OPERATION START #########################
## [START] Install check configuration ##
Checking for existence of the Oracle home location /data01/base/product/11.2.0/dbhome_1
Oracle Home type selected for deinstall is: Oracle Single Instance Database
Oracle Base selected for deinstall is: /data01/base
Checking for existence of central inventory location /data01/orainventory
Checking for sufficient temp space availability on node(s) : 'exdbadm01'
## [END] Install check configuration ##
Network Configuration check config START
Network de-configuration trace file location: /data01/orainventory/logs/netdc_check2021-01-27_08-43-16-PM.log
clsc_ginit: CLSD initialization failed, rc -1, ecode 64
Network Configuration check config END
Database Check Configuration START
Database de-configuration trace file location: /data01/orainventory/logs/databasedc_check2021-01-27_08-43-17-PM.log
Use comma as separator when specifying list of values as input
Specify the list of database names that are configured in this Oracle home [exdbx]:
###### For Database 'exdbx' ######
Specify the type of this database (1.Single Instance Database|2.Oracle Restart Enabled Database) [1]: 1
Specify the diagnostic destination location of the database [/data01/base/diag/rdbms/exdbx]:
Specify the storage type used by the Database ASM|FS []: ASM
Database Check Configuration END
Enterprise Manager Configuration Assistant START
EMCA de-configuration trace file location: /data01/orainventory/logs/emcadc_check2021-01-27_08-46-28-PM.log
Checking configuration for database exdbx
Enterprise Manager Configuration Assistant END
Oracle Configuration Manager check START
OCM check log file location : /data01/orainventory/logs//ocm_check2031.log
Oracle Configuration Manager check END
######################### CHECK OPERATION END #########################
####################### CHECK OPERATION SUMMARY #######################
Oracle Home selected for deinstall is: /data01/base/product/11.2.0/dbhome_1
Inventory Location where the Oracle home registered is: /data01/orainventory
The following databases were selected for de-configuration : exdbx
Database unique name : exdbx
Storage used : ASM
No Enterprise Manager configuration to be updated for any database(s)
No Enterprise Manager ASM targets to update
No Enterprise Manager listener targets to migrate
Checking the config status for CCR
Oracle Home exists with CCR directory, but CCR is not configured
CCR check is finished
Do you want to continue (y - yes, n - no)? [n]: y
A log of this session will be written to: '/data01/orainventory/logs/deinstall_deconfig2021-01-27_08-43-09-PM.out'
Any error messages from this session will be written to: '/data01/orainventory/logs/deinstall_deconfig2021-01-27_08-43-09-PM.err'
######################## CLEAN OPERATION START ########################
Enterprise Manager Configuration Assistant START
EMCA de-configuration trace file location: /data01/orainventory/logs/emcadc_clean2021-01-27_08-46-28-PM.log
Updating Enterprise Manager ASM targets (if any)
Updating Enterprise Manager listener targets (if any)
Enterprise Manager Configuration Assistant END
Database de-configuration trace file location: /data01/orainventory/logs/databasedc_clean2021-01-27_10-26-45-PM.log
Database Clean Configuration START exdbx
This operation may take few minutes.
Database Clean Configuration END exdbx
Network Configuration clean config START
Network de-configuration trace file location: /data01/orainventory/logs/netdc_clean2021-01-27_10-26-59-PM.log
De-configuring backup files...
Backup files de-configured successfully.
The network configuration has been cleaned up successfully.
Network Configuration clean config END
Oracle Configuration Manager clean START
OCM clean log file location : /data01/orainventory/logs//ocm_clean2031.log
Oracle Configuration Manager clean END
Setting the force flag to false
Setting the force flag to cleanup the Oracle Base
Oracle Universal Installer clean START
Detach Oracle home '/data01/base/product/11.2.0/dbhome_1' from the central inventory on the local node : Done
Delete directory '/data01/base/product/11.2.0/dbhome_1' on the local node : Done
Delete directory '/data01/base' on the local node : Done
Oracle Universal Installer cleanup was successful.
Oracle Universal Installer clean END
## [START] Oracle install clean ##
Clean install operation removing temporary directory '/tmp/deinstall2021-01-27_08-41-48PM' on node 'exdbadm01'
## [END] Oracle install clean ##
######################### CLEAN OPERATION END #########################
####################### CLEAN OPERATION SUMMARY #######################
Successfully de-configured the following database instances : exdbx
Cleaning the config for CCR
As CCR is not configured, so skipping the cleaning of CCR configuration
CCR clean is finished
Successfully detached Oracle home '/data01/base/product/11.2.0/dbhome_1' from the central inventory on the local node.
Successfully deleted directory '/data01/base/product/11.2.0/dbhome_1' on the local node.
Successfully deleted directory '/data01/base' on the local node.
Oracle Universal Installer cleanup was successful.
Oracle deinstall tool successfully cleaned up temporary directories.
#######################################################################
############# ORACLE DEINSTALL & DECONFIG TOOL END #############
Clean up the grid directories
[root@exdbadm01 apps01]# ls
base orainventory
[root@exdbadm01 apps01]# rm -rf base/
At last the asm disk headers entries should be erased if asm disks are reused
You can refer this post for more info
https://wordpress.com/post/alphaoragroup.com/1109
Now a fresh software can be installed