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Problem(Abstract) |
In a networked environment, traffic to the DNS can be a
problem. The SDK that ships with IBM® WebSphere® Application Server
provides a DNS caching service to help reduce this traffic. |
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Cause |
The caching function allows an IP address to be stored in
a cache. The IP address is obtained from this cache rather than sending a
request to the DNS server. |
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Resolving the
problem |
The SDK provides the following properties to control
network address caching:
networkaddress.cache.ttl
(default: -1) |
Specified in java™ .security to indicate the caching
policy for successful name look-ups from the name service. The value is
specified as an integer to indicate the number of seconds to cache the
successful look-up.
A value of -1 indicates cache forever.
networkaddress.cache.negative.tll
(default 10) |
Specified in java.security to indicate the caching policy for
unsuccessful name look-ups from the name service. The value is specified
as an integer to indicate the number of seconds to cache the failure for
unsuccessful look-ups.
A value of 0 indicates never cache. A value of -1 indicates
cache forever.
You can also specify these as generic JVM arguments:
This corresponds to the networkaddress.cache.ttl, which has the
same meaning and takes the same values, but can be used as a command-line
option.
sun.net.inetaddr.negative.ttl |
This corresponds to networkaddress.cache.negative.ttl, which has
the same meaning and takes the same values, but can be used as a
command-line option.
Currently there are no recommended guidelines on setting these
parameters. When you select values, consider the following things:
- Reliability of the DNS server
- Impact of DNS traffic on the network
- Lease time interval for dynamic IP addresses
- DNS time to live value
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Cross Reference information |
Segment |
Product |
Component |
Platform |
Version |
Edition |
Application Servers |
Runtimes for Java Technology |
Java SDK |
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