Performance Considerations

The following connection options can enhance driver performance. You can also enhance performance through efficient application design. Refer to Chapter 5 “Designing ODBC Applications for Performance Optimization” in the DataDirect Connect Series for ODBC Reference for details.

Application Using Threads (ApplicationUsingThreads): The driver coordinates concurrent database operations (operations from different threads) by acquiring locks. Although locking prevents errors in the driver, it also decreases performance. If your application does not make ODBC calls from different threads, the driver has no reason to coordinate operations. In this case, the ApplicationUsingThreads attribute should be disabled (set to 0).

NOTE: If you are using a multi-threaded application, you must enable the Application Using Threads option.

Connection Pooling (ConnectionPooling): If you enable the driver to use connection pooling, you can set additional options that affect performance:

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Load Balance Timeout: You can define how long to keep connections in the pool. The time that a connection was last used is compared to the current time and, if the timespan exceeds the value of the Load Balance Timeout option, the connection is destroyed. The Min Pool Size option can cause some connections to ignore this value.

■	Connection Reset: Resetting a re-used connection to the initial configuration settings impacts performance negatively because the connection must issue additional commands to the server.

■	Max Pool Size: Setting the maximum number of connections that the pool can contain too low might cause delays while waiting for a connection to become available. Setting the number too high wastes resources.

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Min Pool Size: A connection pool is created when the first connection with a unique connection string connects to the database. The pool is populated with connections up to the minimum pool size, if one has been specified. The connection pool retains this number of connections, even when some connections exceed their Load Balance Timeout value.

Encryption Method (EncryptionMethod): Data encryption may adversely affect performance because of the additional overhead (mainly CPU usage) that is required to encrypt and decrypt data.

Failover Mode (FailoverMode): Although high availability that replays queries after a failure provides increased levels of protection, it can adversely affect performance because of increased overhead.

Use Current Schema for Catalog Functions (UseCurrentSchema): If your application needs to access database objects owned only by the current user, then performance can be improved. In this case, the Use Current Schema for Catalog Functions option must be enabled. When this option is enabled, the driver returns only database objects owned by the current user when executing catalog functions. Calls to catalog functions are optimized by grouping queries. Enabling this option is equivalent to passing the Logon ID used on the connection as the SchemaName argument to the catalog functions.

Workload Manager: The Workload Manager (WLM) automatically adjusts server resources, such as CPU and memory, based on the service class associated with a DB2 workload. Therefore, an application’s performance is tied to the DB2 workload to which it is assigned and, ultimately, to the service class associated with that workload. The DB2 Wire Protocol driver allows your application to set client information in the DB2 database that can be used by the WLM to classify work. If you know that your database environment uses WLM, coordinate with your database administrator to determine how setting the following options affects performance.

■	Accounting Info: Sets the CURRENT CLIENT_ACCTNG register (DB2 for Linux/UNIX/Windows) or the CLIENT ACCTNG register (DB2 for z/OS) on the server.

■	Application Name: Sets the CURRENT CLIENT_APPLNAME register (DB2 for Linux/UNIX/Windows) or CLIENT APPLNAME register (DB2 for z/OS) on the server.

■	Client Host Name: Sets the CURRENT CLIENT_WRKSTNNAME register (DB2 for Linux/UNIX/Windows) or CLIENT WRKSTNNAME register (DB2 for z/OS) on the server.

■	Client User: Sets the CURRENT CLIENT_USERID register (DB2 for Linux/UNIX/Windows) and CLIENT USERID register (DB2 for z/OS) on the server.

■	Program ID: Sets the CLIENT_PRDID value on the server.