By default, a database driver processes requests synchronously; control is not returned to your application until a function or subroutine call completes. If the driver you are using supports asynchronous processing, your application can request asynchronous processing for the commands in the following list. (All of these commands either submit requests to a data source or retrieve data. These operations may require extensive processing.)
To enable or disable asynchronous processing for these commands, call EDSSetStmtOption and specify ON or OFF for the EDS_ASYNC_ENABLE option. To check the setting of the EDS_ASYNC_ENABLE option, call EDSGetStmtOption.
A command called to perform asynchronous processing on an statement handle generates the return code EDS_STILL_EXECUTING. Until the command has finished processing, your application can only use that statement handle with the command or EDSCancel. If your application calls the command before it has finished processing, the command returns EDS_STILL_EXECUTING. If your application calls the command after it has finished processing, the command returns a different return code, such as EDS_SUCCESS or EDS_ERROR.
After calling a command asynchronously, your application should check the return code before entering a response block. If the return code does not equal EDS_STILL_EXECUTING, do not enter a response block.
