Data Exchange in Prepared Execution
Prepared execution allows you to exchange data between your application and ESQL using SQL descriptor areas or host language variables. An SQL descriptor area (SQLDA) is a data structure that describes and provides storage for input or output column data, and also for parameter marker values. After preparing an SQL request, there are several ESQL statements and functions that you can use to allocate storage for the request and initialize any SQLDAs to complete execution of the request.
If you use host language variables for a request, ESQL ultimately uses an SQLDA to complete the data exchange. If you specify host language variables for dynamic column input or output or for parameter marker values in certain dynamic ESQL statements, the preprocessor generates a default SQLDA that references the specified host language variables for data storage. For more information, see the "SQL Descriptor Area" section in this chapter.
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