On 10R2 if the Oracle binaries are installed with the RAC, one can’t use those binaries to start Oracle Instance if CRS is not running, so in case when one needs to start the instance without CRS one needs to rebuild the oracle and it’s libraries to start the instance.
To turn off RAC
# link the oracle libraries
$ cd $ORACLE_HOME/rdbms/lib
$ make -f ins_rdbms.mk rac_off
# rebuild oracle
$ cd $ORACLE_HOME/bin
$ relink oracle
To turn on RAC
# link the oracle libraries
$ cd $ORACLE_HOME/rdbms/lib
$ make -f ins_rdbms.mk rac_on
# rebuild oracle
$ cd $ORACLE_HOME/bin
$ relink oracle
An Oracle Spin by Alex Lima 
Hi,
Very good short and important tip. Thanks for same.
Excellent for providing very simple trick to enable and disable Oracle RAC. As per my assumption, this trick will be working on every unix and linux. Right?
thanks for providing this
Regards
Hari
Very Nice Concept
Trgards
Kiran