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.