RAC ON and OFF

In some cases, you may want to disable the Oracle RAC options for testing purposes-perhaps to run a benchmark or to convert the Oracle RAC binaries to single-instance binaries.
Convert RAC  - to NON-RAC .Not compatible for windows system only for UNIX system.

Some times usage when CRS (HA) not comming up and getting error " cannot communicate with Cluster ready services " immediately convert RAC TO NON-RAC
Fix the node issue then enable again.

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RAC OFF
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Use the following steps to disable Oracle RAC (known as RAC OFF):

1. Log in as the Oracle software owner (which is typically the UNIX account oracle) in all nodes.

2. Shut down all the instances from all the nodes using a NORMAL or IMMEDIATE option.

3. Change the working directory to $ORACLE_HOME/lib:

cd $ORACLE_HOME/lib


4. Run the following “make” command to relink the Oracle binaries without the Oracle RAC option:

make -f ins_rdbms.mk rac_off


This normally runs for a few minutes and should not pose any errors.


5. Now relink the Oracle binaries:

make -f ins_rdbms.mk ioracle


NOTE:- Now the Oracle binaries are relinked with the RAC OFF option. You may have to edit the init.ora or SPFILE parameters accordingly.
If errors occur in step 4, you may need to contact Oracle Support and log a service request with the trace and log files.



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RAC ON 
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Use the following steps to enable Oracle RAC (known as RAC ON):


1. Log in as the Oracle software owner (typically the UNIX account oracle) in all nodes.

2. Shut down all the instances from all the nodes using a NORMAL or IMMEDIATE option.

3. Change the working directory to $ORACLE_HOME/lib:

cd $ORACLE_HOME/lib


4. Run the following “make” command to relink the Oracle binaries without the RAC option:

make -f ins_rdbms.mk rac_on


This normally runs for a few minutes and should not pose any errors.

5. Now relink the Oracle binaries:

make -f ins_rdbms.mk ioracle


NOTE:- Now the Oracle binaries are relinked with the RAC ON option. You may need to edit the init.ora or SPFILE parameters accordingly.
If any errors occur in step 4, you may need to contact Oracle Support and log a service request with the trace and log files.