Plesk 8.6 on source server uses remote MSSQL server. If remote database is large, the migration is finished successfully, but migrated database will be empty (no tables). Trying to backup the database on the source server is finished with error:
Error: dbbackup failed: Unable to backup database 'DB_NAME' Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. The backup or restore was aborted.`
While executing dbbackup.exe utility timeout is expired after passing 4 minutes.
Use dbbackup.exe from Plesk 9.5 as described here.