Text or image columns are updated two ways:
Embed the new value in the text of an update language command. The advantage of this method is simplicity. The disadvantage is that the application must send the entire value at once. This method may not be appropriate for very large columns (that is, larger than the program can allocate space for). Adaptive Server requires the value to be embedded in the command text, and not passed as a command parameter. Adaptive Server does not allow parameters of type text or image.
Initiate a send-data command (with ct_command) and send the value in chunks with ct_send_data). This method handles values that are larger than the program’s buffer space, but it is more complicated. This method may be more natural than the embedded method for applications that read the value in chunks from an external source such as an operating system file.
An application only updates a text or image column using ct_send_data if it has defined (using ct_data_info) current I/O descriptor settings for the column that it intends to update. The I/O descriptor settings are contained in a CS_IODESC structure. (See “CS_IODESC structure”.) Adaptive Server requires a correctly initialized I/O descriptor to perform the update, and the client application must retrieve the required I/O descriptor settings from the server.
