Actual operations performed in parallel for Oracle databases

If you are confused about the parallel execution of the Oracle database in the actual operations of the Oracle database, you can use the following articles to learn about its practical application and functions. The following is a detailed introduction of the article.

Parallel Execution of Oracle databases

 
 

  
  
session_max_open_files: 
 
 

Description: Maximum number of bfiles that can be opened in any given session. Once this number is reached, more files cannot be opened in the session. This parameter also depends on the operating system parameter MAX_OPEN_FILES.

Value Range: 1-at least (50, MAX_OPEN_FILES on OS ).

Default Value: 10

 
 

  
  
parallel_execution_message_size: 
 
 

Description: This parameter specifies the size of messages in parallel execution (parallel query, PDML, parallel recovery and replication) of the Oracle database. If the value is greater than 2048 or 4096, a larger sharing pool is required. If PARALLEL_AUTOMATIC_TUNING = TRUE, the message buffer is specified outside the large storage pool.

Value Range: 2148-infinity.

Default Value: If PARALLEL_AUTOMATIC_TUNING is FALSE, the normal value is 2148. If PARALLEL_AUTOMATIC_TUNING is TRUE, the value is 4096 (depending on the operating system ).

 
 

  
  
Paralle_min_percent: 
 
 

Description: minimum percentage of threads required for parallel execution. This parameter can be set to ensure that an error message is displayed when no proper subordinate process is available for concurrent execution, and the query is not executed.

Value Range: 0-100

The default value is 0, indicating that this parameter is not used.

 
 

  
  
Parallel_automatic_tuning: 
 
 

Note: if it is set to TRUE, Oracle determines the default value for parameters that control parallel execution. In addition to setting this parameter, you must also set parallelism for the tables in the system.

Value range: TRUE | FALSE

Default Value: FALSE

 
 

  
  
parallel_threads_per_cpu: 
 
 

Note: describes the number of processes or threads that can be processed by a CPU during row-based execution with the Oracle database, and optimizes parallel adaptive algorithms and load balancing algorithms. This value should be reduced if the computer shows signs of overload when performing a typical query.

Value Range: any non-zero value.

Default Value: Depends on the Operating System (usually 2)

 
 

  
  
parallel_broadcast_enabled: 
 
 

Note: by using a hash join or merge join, you can improve performance when connecting multiple large result sets to a small result set (measured in bytes rather than behavior units. If this value is set to TRUE, the optimizer can spread each row in a small result set to each cluster database processing row in a large set.

Value range: TRUE | FALSE

Default Value: FALSE

 
 

  
  
parallel_adaptive_multi_user: 
 
 

Enables or disables an adaptive algorithm to improve the performance of multi-user environments that use parallel execution. The request concurrency is automatically reduced by system load. This function is enabled when the query is started. When PARALLEL_AUTOMATIC_TUNING = TRUE, it works best.

Value range: TRUE | FALSE

Default Value: If PARALLEL_AUTOMATIC_TUNING = TRUE, the value is TRUE; otherwise, the value is FALSE.

 
 

  
  
parallel_max_servers: 
 
 

Description: Maximum number of parallel execution servers or parallel recovery processes of a routine. If necessary, the number of query servers allocated when the routine is started will increase to this number.

Value Range: 0-256

Default Value: CPU_COUNT, PARALLEL_AUTOMATIC_TUNING, and PARALLEL_ADAPTIVE_MULTI_USER.

 
 

  
  
parallel_min_servers 
 
 

Description: Minimum number of query server processes created by Oracle after the startup routine is executed concurrently in the Oracle database.