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Using the Driver : Performance Considerations
  

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Performance Considerations

The following connection options can enhance driver performance. You can also enhance performance through efficient application design. See Designing ODBC Applications for Performance Optimization for details.
Array Size (ArraySize): To improve throughput, consider increasing the value of Array Size. By increasing the value of Array Size, you increase the number of rows the driver will retrieve from the server for a fetch. In turn, increasing the number of rows that the driver can retrieve reduces the number, and expense, of network round trips. For example, if an application attempts to fetch 100,000 rows, it is more efficient for the driver to retrieve 2000 rows over the course of 50 round trips than to retrieve 500 rows over the course of 200 round trips. Note that improved throughput does come at the expense of increased demands on memory and slower response time. Furthermore, if the fetch size exceeds the available buffer memory of the server, an out of memory error is returned when attempting to execute a fetch. If you receive this error, decrease the value specified until fetches are successfully executed.
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.
Default Buffer Size for Long/LOB Columns (DefaultLongDataBuffLen): To improve performance when your application fetches images, pictures, or long text or binary data, a buffer size can be set to accomodate the maximum size of the data. The buffer size should only be large enough to accommodate the maximum amount of data retrieved; otherwise, performance is reduced by transferring large amounts of data into an oversized buffer. If your application retrieves more than 1 MB of data, the buffer size should be increased accordingly.
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 connect as the Schema Name arguement to catalog functions.