B4J Question Boolean Flag Wrong Behavior

Public Sub BackupData(user As String) As Boolean
    Dim flagSuccess As Boolean=False
    lock.WriteLock
Try
    sql.ExecNonQuery2("DELETE FROM databackup WHERE user = ?", Array(user))
    sql.ExecNonQuery2("INSERT INTO databackup xxx SELECT * FROM data WHERE user = ?", Array(user))
    flagSuccess = True
Catch
    Log(LastException)
    'flagSuccess = False
End Try
    lock.WriteRelease
Log("flagSuccess="&flagSuccess)   
    Return flagSuccess
End Sub