A UDF, UDM, or external stored procedure can return an empty LOB value by returning without calling FNC_LobAppend.
The arguments are validated to the extent possible. If an argument is not valid, the request that invoked the UDF, UDM, or external stored procedure fails and typically returns an error that looks like this:
7554 Invalid LOCATOR argument to LOB access function in UDF database_name.udf_name.
Control does not return to the UDF, UDM, or external stored procedure.
FNC_LobAppend needs to be called to populate a LOB that is defined as a column in an output stream of a table operator. Before calling FNC_LobAppend, you must call FNC_LobCol2Loc to obtain the LOB_RESULT_LOCATOR passed as the first argument to FNC_LobAppend.