An application retrieves the I/O descriptor settings by calling ct_data_info. If the SQL Server is version 11.0 or later, or Adaptive Server the application also select the I/O descriptor directly using the server ss.
To retrieve the current I/O descriptor with ct_data_info, an application must first select the column of interest in the row of interest. While processing the row results returned from the select, the application gets the I/O descriptor as follows:
Call ct_fetch to fetch the row of interest.
Call ct_get_data to retrieve the column’s value and refresh the I/O descriptor for the column. To refresh the I/O descriptor without retrieving any data for the column, call ct_get_data with buflen as 0.
Call ct_data_info to retrieve the I/O descriptor.
Beginning with version 11.0, SQL Server, provides an alternative method for setting the I/O descriptor fields. This method is used by applications that only update one text or image column at a time. See “Using global variables to update a text or image column”.
