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Database Connection Pooling

Siebel database Connection Pooling is a feature that allows database connections to be shared and reused, so reducing the number of DB2 database active threads (DBATs) that are required. This feature saves the overhead of creating and maintaining database connections for each user session and allows the number of concurrent user sessions to exceed the number of database connections. Database Connection Pooling is not enabled by default.

About Database Connection Pooling

With Database Connection Pooling, a user session is not tied to a database connection. The Application Object Manager component creates database connections as required. When a new connection is needed (a user session is started), the Application Object Manager creates an initial connection for user authentication. If there are connections in the connection pool, this initial connection is dropped; if the shared connection pool is empty, this initial connection is added to the pool.

When the user issues a query, it is run on any free database connection in the pool and the connection is blocked until the statement has finished running. When the query completes, the connection is returned to the pool and becomes available to run any other user queries. If a number of users issue fast-running queries, they can share the same connection without blocking.

If the user issues a query and all the existing connections are busy, then a new connection is created, provided the pool has less than the maximum number of connections allowed. The value specified for the MaxSharedDbConns server parameter determines the maximum number of database connections that can be created.

When the maximum number of connections is reached, the Application Object Manager randomly checks all existing connections for their availability and assigns the query to the first free connection that it finds. The Application Object Manager keeps track of connection utilization and determines the minimum number of connections that is required depending on statement load.

For additional information on Database Connection Pooling, see Siebel Performance Tuning Guide.

NOTE:  In the current release of Siebel Business Applications, you can cancel user-initiated query operations even if Connection Pooling is turned on.

About Connection Pooling and Cursor Close

Connection Pooling can give you flexibility in increasing the number of rows returned from a query or in keeping cursors open by setting the DSMaxCursorSize parameter to -1. However, consider the latter option only if it is essential to your business needs. Setting the DSMaxCursorSize parameter to the -1 setting requires careful DB2 buffer pool tuning and the use of DB2 storage contraction DSNZPARMs. For further information, see About Cursor Close and DSNZPARM Parameter Settings for Siebel Business Applications.

You must also review the unlimited cursor close values in combination with other factors, such as:

• DB2 DBM1 virtual storage
• Transaction rate of arrival
• Average length of a transaction
• Maximum number of connected threads
• Number of expected long-running complex queries