1. Stop database and CRS on both node
$ srvctl stop database -d mydb
# crsctl stop crs

2. Turn Off RAC

SQL> startup
ORA-29702 error occurred in Cluster Group Service operation

Relink with the RAC OFF.
$ cd $ORACLE_HOME/rdbms/lib
$ /usr/ccs/bin/make -f ins_rdbms.mk rac_off

Relinking oracle
$ make -f ins_rdbms.mk ioracle

## OR , both working fine
$ cd $ORACLE_HOME/bin
$ relink oracle

If ASM Instance Exist, run below command as root
# /oracle/product/10.2.0/db/bin/localconfig delete
# /oracle/product/10.2.0/db/bin/localconfig add

3. Parameter(Pfile/spfile) & database changes
SQL> startup
SQL> alter database disable thread 2;
SQL> alter system set remote_listener='';

3a. Remove unwanted logfile
SQL> select thread#, group# from v$log;
SQL> alter database drop logfile group 3;
SQL> alter database drop logfile group 4;

3b. Remove unwanted tablespace
SQL> drop tablespace UNDOTBS2 including contents and datafiles;

3c. Rename instance name.
SQL> alter system set instance_name=<new_name> scope=spfile;
SQL> shutdown immediate
SQL> startup
- Change your ORACLE_SID environment

4. Run $ORA_CRS_HOME/install/rootdelete.sh on both node
- This will stop and remove all CRS startup related file

5. Remove $ORA_CRS_HOME binary using Clusterware OUI installer
- Ignore any error if 2nd node already down
- rm -rf $ORA_CRS_HOME

6. Modify listener file
$ vi $ORACLE_HOME/network/admin/listener.ora

6a. Modify tnsname file
$ vi $ORACLE_HOME/network/admin/tnsnames.ora

应该还要把初始化参数中的cluster_database改成false

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