ImportFile size limit – PB Docs 2022

PowerBuilder 10.0 and later versions are Unicode enabled. If your
application uses the ImportFile method to import very large text files
(approximately 839,000 lines) into a DataWindow or DataStore, ImportFile
returns the error code -15. Larger text files could be imported in ANSI
versions of PowerBuilder.

NOTE: The release bulletins for
earlier versions listed the size limit for large files as approximately
839,000 lines. The size limit depends on the number of columns, as well
as the number of lines.