Distributed cache updating using dynamic source routing protocol

16 Aug

To execute a query in parallel, Oracle generally creates a producer queue server and a consumer server.The producer queue server retrieves rows from tables and the consumer server performs operations such as join, sort, DML, and DDL on these rows.Parallel execution dramatically reduces response time for data-intensive operations on large databases typically associated with decision support systems (DSS) and data warehouses.You can also implement parallel execution on certain types of online transaction processing (OLTP) and hybrid systems.Each communication channel has at least one, and sometimes up to four memory buffers.Multiple memory buffers facilitate asynchronous communication among the parallel execution servers.For example, a bank might use parallelized batch programs to perform millions of updates to apply interest to accounts.

distributed cache updating using dynamic source routing protocol-7

If all parallel execution servers in the pool are occupied and the maximum number of parallel execution servers has been started, the parallel execution coordinator switches to serial processing.Figure 21-1 illustrates message buffers and how producer parallel execution servers connect to consumer parallel execution servers.Text description of the illustration dwhsg096When a connection is between two processes on the same instance, the servers communicate by passing the buffers back and forth.When a user issues a SQL statement, the optimizer decides whether to execute the operations in parallel and determines the degree of parallelism (DOP) for each operation.You can specify the number of parallel execution servers required for an operation in various ways.