Hello,
I do a backup service with FIBPlus 4.7.0 Delphi components on a very
fragmented database (lots of delete operations have been done on it,
450 MB file).
Here is a sample code:

with BackUpService do
begin
BackUpFile.Text := 'tmpbackup.fbk';
LoginPrompt := False;
Options := [IgnoreLimbo];
Protocol := TCP;
DataBaseName := 'c:\db.fdb';
ServerName := 'x.x.x.x';
Params.Append('user_name=sysdba');
Params.Append('password=masterkey');
Active := True;
ServiceStart;
while not Eof do
GetNextChunk; //or GetNextLine
end;

It always hangs when progress is about 98% (no matter if database is
on my local computer or on a remote one). Task manager shows Firebird
service uses 99% CPU. It doesn't hang if I do backup with gbak (using
the same backup options). Moreover the program doesn't hang on the
same database after backup and restore with gbak. If I add some
records to some tables after restoring with gbak I still can do
backup with my program (the database is less fragmented).
I've checked it with IBExpert program and IBExpert hangs in the same
moment my program does. Is there a bug in Firebird 1.5.1 backup
service? Please for any answer. Thank you in advance.

Best regards
Jaroslaw