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Configuring Pooling for Specialized Database Connections

Specialized database connections, which are not shared, are used primarily by specialized Siebel components such as Siebel eAI that need transactions to span multiple AOM operations. These connections are used for operations that use BEGIN TRANSACTION and END TRANSACTION.

Configuring Parameters for Pooling Specialized Connections

This section describes how to enable or disable specialized connection pooling using the parameter MinTrxDbConns (DB Multiplex - Min Number of Dedicated DB Connections).

• MinTrxDbConns controls the minimum number of specialized database connections for each multithreaded process. The connections are not created until they are needed. The minimum value is thus the minimum size of the pool of specialized connections once all the connections in the pool have been created.
  • To enable specialized connection pooling, set MinTrxDbConns to a positive integer value (at least 1). You must also configure pooling for default database connections.
  • To disable specialized connection pooling, set MinTrxDbConns to -1 (this is the default value).
• There is no explicit limit to the maximum number of specialized connections. However, effectively, there cannot be more specialized connections than sessions. On average, there will be many fewer connections than sessions.

MinTrxDbConns is defined per AOM component, on an enterprise basis (this parameter is included in named subsystems of type InfraDatasources). The database connections this parameter controls are not shared across multithreaded processes. The actual minimum number of specialized database connections for each multithreaded process is what you specify as the value for MinTrxDbConns.

NOTE:  MinTrxDbConns works differently than MaxSharedDbConns and MinSharedDbConns, which specify the number of shared database connections available for the entire AOM. For details, see Configuring Pooling for Default Database Connections.

Example Configuration for Pooling Specialized Connections

Assume, for example, the following parameter setting, in addition to those described in Example Configuration for Pooling Default Connections:

MinTrxDbConns = 5

With this setting, each multithreaded process would have a minimum of five specialized database connections. If all five multithreaded processes are running on this AOM, there would be a minimum of 25 specialized connections for this AOM.

How Pooled Specialized Connections Are Assigned

When the AOM starts up, the specialized connection pool is empty. When a request is made to start a transaction, the AOM requests a database connection from the specialized connection pool. If one is available, it is removed from the pool and given to the session for that session's exclusive use.

When the transaction completes (such as by being committed or canceled), the session returns the specialized connection to the pool. If the pool already contains more than the number of connections specified by MinTrxDbConns, the specialized connection is closed; otherwise, it is retained in the pool.

Scenario for Assigning Pooled Specialized Connections

Assume, for example, that MinTrxDbConns is set to 2. Specialized connections will be handled as follows:

• User 1 starts Transaction 1. The specialized connection pool is empty, so a new connection is created. Once Transaction 1 completes, this connection is returned to the pool.
• User 2 starts Transaction 2. If Transaction 1 is still running, then a new specialized connection is created. If Transaction 1 completed, then Transaction 2 uses the first database connection.
• When two specialized connections have been created, they will remain in the pool until the AOM terminates.