Oracle11gRAC跨節點 並行查詢的控制

Oracle11gRAC跨節點並行查詢的控制，跟先前的版本有所變化：

引數instance_groups被廢棄，並新增加了引數：PARALLEL_FORCE_LOCAL來限制內部節點的並行操作．

使用Services來確定並行查詢將在哪些節點上執行．

引數PARALLEL_INSTANCE_GROUP設定為Service的名稱.

 

下為官方說明：

 

By default, in an Oracle RAC environment, a SQL statement executed in parallel can
run across all of the nodes in the cluster. For this cross-node or inter-node parallel
execution to perform. well, the interconnect in the Oracle RAC environment must be size appropriately because inter-node parallel execution may result in a lot of interconnect traffic. To limit inter-node parallel execution, you can control parallel
execution in an Oracle RAC environment using the PARALLEL_FORCE_LOCAL
initialization parameter. By setting this parameter to TRUE, the parallel execution
servers can only execute on the same Oracle RAC node where the SQL statement was started.

Services are used to limit the number of instances that participate in a parallel SQL
operation. When the default database service is used, the parallel SQL operation can run on all available instances. You can create any number of services, each consisting of one or more instances. When a parallel SQL operation is started, the parallel execution servers are only spawned on instances which offer the specified service used in the initial database connection.

PARALLEL_INSTANCE_GROUP is an Oracle RAC parameter that, when used in
conjunction with services, lets you restrict parallel query operations to a limited
number of instances.To restrict parallel query operations to a limited number of instances, set the PARALLEL_INSTANCE_GROUP initialization parameter to the name of a service. This does not affect other parallel operations such as parallel recovery or the processing of GV$ queries.

 

 

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