PURPOSE 
--------  
To provide a list of parameters that are relevant to parallel 
query, Parallel DML and other operation which can be parallized. 
We also suggest values for some init.ora parameters to have a good  
starting point. 
 
 
SCOPE & APPLICATION 
------------------- 
This note is intended for DBAs who are considering using PX 
  
Initialization parameters 
------------------------- 
The following parameters are currently affecting the behavior 
of Parallel Execution in Oracle: 
 
 
Parameters important for setup 
------------------------------- 
PARALLEL_ADAPTIVE_MULTI_USER                     [NOTE:68594.1] 
PARALLEL_AUTOMATIC_TUNING   (Deprecate in 10G)   [NOTE:68595.1] 
PARALLEL_BROADCAST_ENABLED  (Obsolete in 9.2)    [NOTE:68596.1] 
PARALLEL_EXECUTION_MESSAGE_SIZE                  [NOTE:68598.1] 
PARALLEL_MAX_SERVERS                             [NOTE:30790.1] 
PARALLEL_MIN_PERCENT                             [NOTE:39034.1] 
PARALLEL_MIN_SERVERS                             [NOTE:30791.1] 
PARALLEL_THREADS_PER_CPU                         [NOTE:68604.1] 
OPTIMIZER_PERCENT_PARALLEL (Obsolete in 9i)      [NOTE:39027.1] 
 
Parallel Execution and the use of Memory 
---------------------------------------- 
LARGE_POOL_SIZE                                  [NOTE:47334.1]   
SHARED_POOL_SIZE                                 [NOTE:30810.1] 
 
See also  
[NOTE:238680.1] Parallel Execution the Large/Shared Pool  and ORA-4031 
for more background information.     
 
 
In a Parallel Server or RAC environment, the behavior of parallel  
query and PDML is affected by the following parameters also: 
------------------------------------------------------------------ 
PARALLEL_INSTANCE_GROUP                          [NOTE:47351.1] 
INSTANCE_GROUPS                                  [NOTE:47331.1] 
 
 
Parallelism  and Recovery 
------------------------- 
FAST_START_PARALLEL_ROLLBACK                     [NOTE:68932.1] 
RECOVERY_PARALLELISM                             [NOTE:30795.1] 
 
 
Recommeneded Values for PX init.ora Parameter 
--------------------------------------------- 
 
We would suggest the following for a good starting point with PX. 
Maybe some parameter have to be tuned after a while. 
 
Versions prior to 10G. 
 
	set parallel_automatic_tuning=true 
	unset parallel_max_servers 
	unset parallel_min_servers 
	unset parallel_execution_message_size* 
	maybe set parallel_adaptive_multi_user=false** 
 
Version 10G and later 
 
	unset parallel_max_servers 
	unset parallel_min_servers 
	set parallel_execution_message_size=4096 if adequate memory 
	maybe set parallel_adaptive_multi_user=false** 
 
* Machines with enough memory can afford to have higher values 
here like 8k and 16k but the performance "knee" is at 8k, so higher values 
don't give as much benefit. 
 
**This parameter defaults to false unless parallel_automatic_tuning = true.  
In 10G it defaults to true. 
Users may want to set it to false if they wish to perform first come 
first served resource allocation and/or have a queuing mechanism which 
submits jobs to the db. 
 
REFERENCES 
----------- 
Oracle8i Migration  Release 3 (8.1.7) Part Number A86632-01 
Oracle9i Database Migration Release 2 (9.2) Part No. A96530-02