As you know sometimes we need to change CPU count dynamically on our prod systems.

Our Unix team change our 2 node RAC system (11.2.0.3 version) server’s CPU from 20 to 30 on AIX 7.1

After that change one of the instance(node 2) goes down with below error messages:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00068: invalid value 6360 for parameter parallel_max_servers, must be between 0 and 3600
CKPT (ospid: 22135): terminating the instance due to error 2097

After makes some search, to be sure We rised SR 1.

Here is the answers:
Our The Default Value of the parallel_max_servers is calculated based on the Following Equation :

PARALLEL_THREADS_PER_CPU * CPU_COUNT * concurrent_parallel_users * 5

as per : http://docs.oracle.com/cd/E11882_01/server.112/e40402/initparams186.htm#REFRN10158

and the maximum value for this parameter is 3600 , so in some times this equation can lead to higher values than 3600

Please Perform the following Action Plan to resolve this issue :

1- Lower the Value of parallel_max_servers parameter to a reasonable value , for example (10) :

SQL> alter system set parallel_max_servers=300 scope=both sid=’*’ ;

or

2- Apply Patch 13743987

If a system has a high CPU count and there is no value set for parallel_max_servers then the system may try to set the default value of the parallel_max_servers parameter higher than is allowed.
eg:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00068: invalid value 6360 for parameter parallel_max_servers, must be between 0 and 3600

This can cause an instance shutdown if the number of system CPUs alters dynamically.
eg:
The alert log may show a dynamically detected change of CPU count:
Detected change in CPU count to 159
* Load Monitor used for high load check
* New Low – High Load Threshold Range = [152640 – 203520]
Errors in file /…/trace/+ASM2_ckpt_22135.trc:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00068: invalid value 6360 for parameter parallel_max_servers, must be between 0 and 3600
CKPT (ospid: 22135): terminating the instance due to error 2097