Oracle7 Server Tuning

Managing the Query Servers

When you start your instance, the Oracle Server creates a pool of query server processes available for any query coordinator. The number of query server processes that the Oracle Server creates at instance startup is specified by 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.

Varying Pool of Query Server Processes

If the volume of SQL statements processed concurrently by your instance changes drastically, the Oracle Server automatically changes the number of query server processes in the pool to accommodate this volume.

If this volume increases, the Oracle 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 Oracle 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 Oracle Server does not reduce the size of the pool below the value of PARALLEL_MIN_SERVERS regardless of 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. "Tuning the Query Servers"

describes how to monitor an instance's pool of query servers and determine the appropriate values of the initialization parameters.