First, be aware that DP 6.11 is no longer supported
I would suspect that, if it has not already happend, you will get a Disk Agent of Medi Agent timeout
If not, you will probably have to abort this backup
I believe that the root cause for this problem is that you need to implement KeepAlive on your Disk Agents and Media Agents. I have put the discussions in 3 different discussions, depending on the type of servers involved.
THese values would be correct for a Linux system. While your cell Manager is Linux, nothing is said about your clients he Disk Agent (the system being backed up), or the Media Agent, the system that controls the tape drive
Also, it is not enough to just implement the KeepAlive parameters, you also need to add OB2IPCKEEPALIVE=1 into the 'omnirc' file on each server
Finally, it was found out that OB2IPCKEEPALIVE was not working on Linux systems, this was fixed with the upgrade to DP 7.03. Since you are running DP 6.11, this fix will not apply to you