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Configuring Pooling for Default Database Connections

This topic is part of Configuring Database Connection Pooling for Siebel Application Object Managers.

Default database connections can be used by most Siebel Application Object Manager operations.

Configuring Parameters for Pooling Default Connections

The following information describes how to enable or disable pooling for default database connections using the parameters MaxSharedDbConns (DB Multiplex - Max Number of Shared DB Connections) and MinSharedDbConns (DB Multiplex - Min Number of Shared DB Connections).

• To enable connection pooling, set MaxSharedDbConns and MinSharedDbConns to positive integer values (at least 1) that are no higher than MaxTasks minus 1. A connection will be shared by more than one user session once the number of sessions within the multithreaded process exceeds the maximum number of shared connections allowed per process.
  • MaxSharedDbConns controls the maximum number of pooled database connections for each multithreaded process.
  • MinSharedDbConns controls the minimum number of pooled database connections the Siebel Application Object Manager tries to keep available for each multithreaded process.

    The setting of MinSharedDbConns must be equal to or less than the setting of MaxSharedDbConns. Depending on your Siebel Application Object Manager usage patterns, you can set these to the same value or set MinSharedDbConns to a lower value (if you determine this to be helpful in conserving database connection resources).

• To configure persistent and shared database connection pooling, set MaxSharedDbConns, using the appropriate ratio of MaxTasks divided by MaxSharedDbConns. Depending on the ratio, a greater or lesser degree of sharing will be in effect. Start with a 2:1 (or smaller) ratio for MaxTasks divided by MaxSharedDbConns. With this example ratio, two user tasks will share the same database connection.
• To configure persistent but nonshared database connection pooling, set MaxSharedDbConns = MaxTasks minus 1.
• To disable connection pooling, set MaxSharedDbConns and MinSharedDbConns to -1 (this is the default value).

MaxSharedDbConns and MinSharedDbConns are defined per Siebel Application Object Manager component, on an enterprise basis (these parameters are included in named subsystems of type InfraDatasources). The database connections these parameters control are not shared across multithreaded processes. The actual maximum number of database connections for each multithreaded process is determined by the ratio MaxSharedDbConns divided by MaxMTServers.

NOTE:  MaxSharedDbConns and MinSharedDbConns work differently than MinTrxDbConns, which specifies the number of shared specialized database connections available for each multithreaded process. For details, see Configuring Pooling for Specialized Database Connections.

Example Configuration for Pooling Default Connections

Assume, for example, the following parameter settings:

MaxTasks = 500
MaxMTServers = 5
MinMTServers = 5
MaxSharedDbConns = 250
MinSharedDbConns = 250

With these settings, the Siebel Application Object Manager component can support a maximum of 500 tasks (threads). Those 500 tasks would be spread over five multithreaded processes, each having 100 tasks. Each multithreaded process would have a maximum of 50 shared database connections, each of which would serve up to two tasks.

How Pooled Default Connections Are Assigned

When a user logs into the Siebel Application Object Manager, a database connection is established to authenticate the user, then discarded (closed) once the database or external authentication system authenticates the user. After successful authentication, the Siebel Application Object Manager's connection manager checks the connection pool for SQL statements. If this connection pool is empty, then the connection manager adds a connection.

Each time a user initializes a SQL statement, the connection manager checks the connection pool for available connections. The connection manager reserves a connection for the SQL statement in one of the following ways:

• If a connection is available to handle the SQL statement, then the connection manager assigns this connection to execute the SQL statement.

  The connection manager reserves this connection until execution of the SQL statement terminates. On termination of the SQL statement, the connection manager releases the connection. At the end of a user session (due to a user logging out or session timeout), the connection manager checks the connection used by the user session. If this connection is not referenced by other user sessions and the number of connections available in the pool of database connections exceeds the value specified by MinSharedDbConns, then the connection manager closes this connection and releases it from the pool of database connections.

• If no connection is available in the connection pool, then the connection manager creates a new connection and assigns it to execute the SQL statement.

  The connection manager continues to add connections to the connection pool until the number of connections in the connection pool equals MaxSharedDBConns.