• How to manually run LiveUpdate in Backup Exec 11d and above to verify what hotfixes or service packs have already been installed or what updates are available for installation. http://www.symantec.com/docs/TECH50132
• How to check the version or status of the Remote Agent for Windows Servers (RAWS) on remote servers from the Backup Exec Graphical User Interface (GUI)
  http://www.symantec.com/docs/TECH15524

2. Verify no other application is either using or blocking TCP Port 10000 on the media server or remote machine(s).

• Backup Exec Remote Agent for Windows Servers service fails to start, with the error: "Error 3: The system cannot find the path specified."
  http://www.symantec.com/docs/TECH37255
• How to determine the Network Data Management Protocol (NDMP) port status on the remote Linux (Redhat) system in Backup Exec for Windows Servers.
  http://www.symantec.com/docs/TECH48522
• When backing a server with the ISA 2004 Firewall running in the environment, the backup fails with "A communications failure has occurred" and "The connection to target system has been lost”.
  http://www.symantec.com/docs/TECH72800  
• If required, refer to following technote about Firewall and Ports: http://www.symantec.com/docs/TECH43579   

3. Make sure the DCOM Permissions are configured per the following:

• Backup Exec Remote Agent for Windows Servers (RAWS) terminates while backing up any resource on a remote server: with error "The connection to target system has been lost." if DCOM Permissions are not configured properly.
  http://www.symantec.com/docs/TECH65785

4. Confirm the Network Card Drivers are at the latest version on both the media server and each remote machine being backed up. Make sure also the drivers/firmware are up to date on all of each machine's hardware (i.e.: SCSI/Raid Controller, Host Bus Adapter, Motherboard, etc...).

5. Run a disk defragment operation and the Windows Error Checking Utility (CHKDSK /F).

• How to correct slow backups and agent initialization problems on fragmented Windows Server Hard Disk Partitions.
  http://www.symantec.com/docs/TECH11562

6. Review what is installed in the Control Panel, Add/Remove Programs Applet. No other backup or open file technology applications (i.e.: Legato, ArcServe, NetBackup, St. Bernards Open Transaction Manager, etc...) should be installed on the machine, even if these applications are disabled and not being currently used.

7.  If a database application is being backed up when the Remote Agent's Connection is terminated, make sure the application (i.e.: Exchange, Lotus Domino, Oracle, SharePoint, or SQL) is not running a native backup (i.e.: SQL Dump or Exchange Backup with NT Backup) or any other type of maintenance. Make sure also the anti-virus scanner software is not improperly scanning the file system at any time or attempting to run a scan or update at the same time the backup is running. Review the following documents for more information:

Virus scanning recommendations for computers that are running Windows Server 2003, Windows 2000, or Windows XP
http://support.microsoft.com/kb/822158  

Microsoft Exchange mailboxes backed up via the Microsoft Exchange Agent hang in random locations within the backup set
http://www.symantec.com/docs/TECH31648

Slow backup occurs when backing up Microsoft Exchange 2000 and Exchange 2003 servers between 1:00 am and 5:00 am
http://www.symantec.com/docs/TECH17020

"A communications failure has occurred" is reported while performing a multi-stream Oracle backup if the number of ports opened on the firewall are less than the number of streams specified in the backup job
 http://www.symantec.com/docs/TECH55975

8. Make sure the media server and each remote machine has enough physical RAM (Random Access Memory) available to accommodate all the applications running. A backup is a very I/O Intensive Operation on a system, even if the machine is just a member server or workstation in a domain and has no other applications installed on it. Installing the Advanced Open File Option (AOFO), anti-virus scanning software, transactional database applications, and/or promoting a server to a domain controller all require more memory for all the applications to function properly, in addition to the backup software (i.e.: media server or Remote Agents). A restore operation is also more I/O Intensive than a backup, because of the need to both read and write the data, verses just writing the data to a media during a backup. Confirm also the memory is not mis-matched (i.e.: different makes/model) and is what the server hardware manufacturer recommends/supports.

9. Confirm disk compression is not enabled on the hard disks:

How hard disk compression can affect backup and restore jobs on a Windows NT File System Partition
http://www.symantec.com/docs/TECH34346

10. Confirm the Windows Automatic Updates are not set to automatically download or install patches at a time when a backup could possibly be running.

11. Run test backups of each resource (C$, System State, Shadow Copy Components, Databases, etc...) individually using a new Selection List to determine what is being backed up when the Remote Agent terminates. If the Advanced Open File Option (AOFO) is installed and the option is selected during a backup, deselect this option for testing purposes to determine if the backups complete successfully when AOFO is not selected.

12. When backing up to tape hardware, make sure that the Preferred Configuration is set to the default and that none of the modes are selected unless the tape hardware is attached to fibre. For more information on this, review the following document:

Tape Drive Configuration Settings available in Backup Exec for Windows Servers (BEWS)
http://www.symantec.com/docs/TECH91959

13. Lower the priority of the Remote Agent per what shows in the following:

How to change the priority level of the Backup Exec Remote Agent for Windows Servers
http://www.symantec.com/docs/TECH23415 

14. If the connection is terminated during a restore, confirm the target machine has enough free disk space available. Some restore operations require there be 1.5 to 2 times the amount of free disk space to be available than what the amount of data being restored is. The more current versions of database applications also will write some type of useful diagnostic error or warning to the Application Event Viewer Log, so review it too.

Please note: If the Backup Exec Remote Agent Service does not terminate during a backup or restore, but the "connection to the target system has been lost" error still occurs, the issue is most likely occurring because of the network connectivity equipment or configuration (misconfigured DNS, Security Credentials, etc...) between the media server and remote machine(s). Review the following Microsoft Knowledge Base Article and Symantec Knowledge Base Article below and in the Related Documents Section for more information on how to resolve the network connectivity and security issues:

Advanced network adapter troubleshooting for Windows workstations.
http://support.microsoft.com/default.aspx?scid=kb;en-us;325487

Attempting to back up from other servers on the network, the job may fail with the error "0xe00084f8 - The network connection to the Backup Exec Remote Agent has been lost." if the network connection is not configured properly.
http://www.symantec.com/docs/TECH61034

"Access denied" and "access is denied" messages in Backup Exec for Windows Servers and how to troubleshoot the errors
http://www.symantec.com/docs/TECH30739

15. If using IPv6 to back up a remote computer, then the backup may fail. This is a known limitation. For more information, see http://www.symantec.com/docs/TECH169685.