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