Oracle7 Server Administrator's Guide
Managing Processes for the Parallel Query Option
This section describes how, with the parallel query option, Oracle7 can perform parallel processing. In this configuration Oracle7 can divide the work of processing certain types of SQL statements among multiple query server processes. The following topics are included:
See Also: For more information about the parallel query option, see the Oracle7 Server Tuning manual.
Managing the Query Servers
When you start your instance, the Oracle7 Server creates a pool of query server processes available for any query coordinator. Specify the number of query server processes that the Oracle7 Server creates at instance startup via the initialization parameter PARALLEL_MIN_SERVERS.
Query server processes remain associated with a statement throughout its execution phase. When the statement is completely processed, its query server processes become available to process other statements. The query coordinator process returns any resulting data to the user process issuing the statement.
Variations in the Number of Query Server Processes
If the volume of SQL statements processed concurrently by your instance changes drastically, the Oracle7 Server automatically changes the number of query server processes in the pool to accommodate this volume.
If this volume increases, the Oracle7 Server automatically creates additional query server processes to handle incoming statements. The maximum number of query server processes for your instance is specified by the initialization parameter PARALLEL_MAX_SERVERS.
If this volume subsequently decreases, the Oracle7 Server terminates a query server process if it has been idle for the period of time specified by the initialization parameter PARALLEL_SERVER_IDLE_TIME. The Oracle7 Server does not reduce the size of the pool below the value of PARALLEL_MIN_SERVERS, no matter how long the query server processes have been idle.
If all query servers in the pool are occupied and the maximum number of query servers has been started, a query coordinator processes the statement sequentially.
See Also: For more information about monitoring an instance's pool of query servers and determining the appropriate values of the initialization parameters, see the Oracle7 Server Tuning manual.