i want to change the charset of an existing database from none to utf8,

it seems that the safest way is to create a new one then pump data to it .

i have tried two methods  both gave me the same error .

1 - recreate a new database with utf8 charset , then create a simple stored procedure to pump data via "execute block on external datasource"

2 - use fbclone with this command line

fbclone -l fbembed.dll -v -s source.gdb -t destination.gdb -u SYSDBA -p masterkey -tc UTF8 -wc UTF8

both gave me mailformed string error, and a most of rows were not copied to the destination database... 

exemple verbose error

Incompatible column/host variable data type

GDS Code: 335544569 - SQL Code: -303 - Error Code: 249

fields values ---

VANUM = 244458

RUBNUM = 5054

VALEUR = Absence de germes pathogènes.

ATBANA =

DATEMODIF = 16/05/2018

any help is welcome thanks