oracle服务硬件升级---调整参数

author：skate

time：2010-05-13

1)If memory increases and you're 64-bit,  e.g  8G to 16G,  Oracle SGA and related parameters need adjust; So are some the Unix kernel parameters.

2)As for CPU related configuration,  some  parameters, based on CPU_count,  need to adjust,
    * cpu_count
    * fast_start_parallel_rollback
    * parallel_max_servers
    * log_buffer
    * db_block_lru_latches

Please read below:
"Why is cpu_count important?

The Oracle cpu_count is determined when you start Oracle.  The cpu_count affects the Oracle cost-based optimizer through many calculated parameters that use cpu_count as their basis and are considered every time that Oracle creates an execution plan for a SQL statement.  A doubled setting for cpu_count can result in changes to your explain plans when moving from a single to multiple CPUs or when you increase the number of CPUs in your system.

The cpu_count is used to determine the settings for several important init.ora parameters:

·         fast_start_parallel_rollback - The default value is 2 times the number of CPU of your system, but some DBAs recommend setting this value to 4 times the cpu_count.

    *   db_block_lru_latches – This defaults to the following formula : (CPU_COUNT x 6) or (DB_BLOCK_BUFFERS/50), whichever is less. In earlier releases it defaulted to CPU_COUNT/2.  If you set DB_BLOCK_LRU_LATCHES higher than this max value on systems where it is available (<9i) or set the undocumented parameter _DB_BLOCK_LRU_LATCHES higher, then Oracle just ignores this and sets it internally to the above calculated value. However it will be set to Num_pools x (CPU_COUNT/2) if multiple buffer pools (default, recycle, keep and any of the multi-block size pools) are setup.
      
    *     parallel_max_servers - This parameter controls the maximum number of OPQ factotum processes (p000, p001) that are spawned during a parallel query when parallel_automatic_tuning is enabled. The DEFAULT degree of parallelism is calculated as:

                   CPU_COUNT * PARALLEL_THREADS_PER_CPU

·         log_buffer and redo copy patches - The number of CPUs is used to determine the value of log_buffer if the log_buffer parameter is not set in the initialization parameters. For details on LGWR, click here.  There is still argument about whether the cpu_count influences the behavior of actions against the log_buffer. Of course other important internalized parameters that deal with the log buffer are redo copy latches (2 times the number of CPUs when cpu_count>1) and redo allocation latches."

http://www.dba-oracle.com/oracle_tips_cpu_count_wrong.htm

3)If CPU number increases,  your oracle licensing need to update if your license is based on CPU numbers.

Please refer
http://www.oracle.com/corporate/pricing/multicore_faq.pdf

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