Hi Choon Fatt,
The error "Can't open a connection to site 'SYB_BACKUP' Means that there is something missing in your setup.
Run the following:
1>select srvnetname from sysservers where srvname='SYB_BACKUP'
2>go
Check the Value for column "srvnetname". This should equal your backup server name. If not, then you need to update this column
1>sp_configure 'allow updates',1
2>go
1>update sysservers set srvnetname='backup_server_name' where srvname='SYB_BACKUP'
2>go
Check to see that you have connect to backup server
1>SYB_BACKUP...sp_who
2>go
If it returns values and not error then you have a valid connect and you should be able to dump the database.
If not then check your interfaces file to make sure there is an entry for the backup server
Turn off allow updates to system tables:
1>sp_configure 'allow updates',0
2>go