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
7200
# cat /proc/sys/net/ipv4/tcp_keepalive_intvl
75
# cat /proc/sys/net/ipv4/tcp_keepalive_probes
9
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
600
# cat /proc/sys/net/ipv4/tcp_keepalive_intvl
60
# cat /proc/sys/net/ipv4/tcp_keepalive_probes
20
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
OB2IPCKEEPALIVETIME
OB2IPCKEEPALIVEINTERVAL
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