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Data Protector - Support Tip -Linux Only -Using KeepAlive to resolve Timeouts

Many problems encountered with Data Protector can be helped by using the KeepAlive functionality.  These include Disk Agent and Media Agent timeouts, and backups seeming to ‘Complete’, but, never actually finishing.  You may even see Session Statistics printed, but don’t get the popup when the session is completed


The keepalive parameter just turns on the system mechanism for keeping a network connection alive for all the connections we make


The keepalive packets are part of the TCP protocol on machines, and are transparent to the program opening or using the connection.  They are handled by the system and are not seen by application.  They normally default to 7200 seconds, or 2 hours.


In certain circumstances, it is important that  Gateways using TCP/IP socket communications periodically send TCP messages even if they have nothing to say.  These null messages called “keepalive” packets and help inform networking infrastructure that the endpoints are still there, connected, and expect the TCP/IP socket to stay connected even though at the moment, they don’t have any data to exchange. 


On the server where you are seeing the problem, edit the file


/opt/omni/.omnirc                 The ‘dot’ is part of the filename


This file does not exist by default.  If you have this file, you can edit it, and, if not, you can create it using the Linux ‘touch’ command


            touch /opt/omni/.omnirc


  Either way, add this line to the file:


            OB2IPCKEEPALIVE=1                              Activates the KeepAlive mechanism


After making the changes to the ‘omnirc’ file, save the file, making sure that it has no extension, like ‘txt’ or TMPL’


Note:  This functionality for Linux is only available after installing the patch bundle to upgrade to DP 7.03


So, for example, after adding the KeepAlive switch to the ‘omnirc’ file, you need to set the kernel parameters to change the default value of 7200 seconds.


When you are using Linux, you set the kernel parameters this way; You can see the current values in this manner


# cat /proc/sys/net/ipv4/tcp_keepalive_time



  # cat /proc/sys/net/ipv4/tcp_keepalive_intvl



  # cat /proc/sys/net/ipv4/tcp_keepalive_probes



These are the default values. To set these correctly,


  # echo 600 > /proc/sys/net/ipv4/tcp_keepalive_time


  # echo 60 > /proc/sys/net/ipv4/tcp_keepalive_intvl


  # echo 20 > /proc/sys/net/ipv4/tcp_keepalive_probes


and run this again to be sure the parameter is set correctly

# cat /proc/sys/net/ipv4/tcp_keepalive_time



  # cat /proc/sys/net/ipv4/tcp_keepalive_intvl



  # cat /proc/sys/net/ipv4/tcp_keepalive_probes



In this example, the above settings will cause keepalive packets to be sent every minute.   If a response it not receive it will resend the keepalive packet every 5 seconds.  After 60 seconds, it will reset the socket connection if 20 keepalives fail to get through.  This allows a cable to be disconnected and reconnected for up to 30 seconds without dropping the connection, but it will also re-connect in less than 2 minutes if a device reboots or shuts down without properly closing the TCP/IP socket 


The key is to set these Values low because most firewalls, etc. timeout after an hour or so.  Having the interval set to 15 or even 30 min. should not hurt anything.


You may have seen some reference to the ‘omnirc’ environment values





It needs to be emphasized that OB2IPCKEEPALIVETIME and OB2IPCKEEPALIVEINTERVAL are used on Windows servers only, and have no effect on HPUX or Linux servers


If you want to add this line to the .omnirc’ file proactively, and set the kernel parameters,, that is, without seeing the problem, this is acceptable to cut off a possible future problem.


Typically, you only need to set KeepAlive on Disk Agents and Media Agents.  It is usually not a requirement to set this on a cell manager unless it is also a Media Agent which is timing out.


Up to this point, we have seen no negative effects to setting KeepAlive on HPUX servers



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