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Easy Learn Java: Programming Articles, Examples and Tips - Page 127


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When I use InetAddress.getByName if a lookup to the name service failed then all

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Question: When I use InetAddress.getByName if a lookup to the name service failed then all subsequent lookups of that hostname fail as well for the lifetime of the virtual machine...
It looks like negative lookups are cashed. What is solution? Is it more bugs I should be aware of?

Answer: Use latest J2SE 1.4! Prior to J2SE 1.4 negative lookups were always cached. This has changed in 1.4 so that by default if a lookup fails it's possible for a subsequent lookup to succeed. This is particularly important in dial-up environments or environments where the name service is not reliable.

Also prior to J2SE 1.4.1 the java.net.InetAddress.getLocalHost() would cache the lookup of the IP address of the local machine for the entire session of the application. This behavior poses a problem for applications running on machines that are connected to the internet via a dial-up connection or machines that acquired their addresses through DHCP. This has been corrected in 1.4.1 so that the local IP address is no longer cached. InetAddress.getLocalHost() will return the correct IP address for dial-up connections as well as for DHCP.

Prior to J2SE 1.4 the InetAddress.toString() would perform a lookup via the name service if the hostname wasn't previously resolved. This is no longer the case in 1.4 and toString will return immediately. If the hostname is not resolved the returned string will contain the dotted IP address only.
Applications that depend on toString() returning a string with the resolved hostname should be aware of this correction in 1.4

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5 comments | Printer Friendly Page  Send to a Friend | Score: 5
Posted by jalex on Monday, January 12, 2004 (00:00:00) (5644 reads)

Replication Monitoring Center for DB2

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Replication Monitoring Center for DB2 is a software tool that supports DB2 replication supervision. It is used atop DB2 DataPropagator, the DB2 UDB data replication feature. The Replication Monitoring Center for DB2 is used to supervise replication scenarios, reporting configuration, and operational data to the user. The tool significantly reduces the time and cost for replication monitoring and operational administration.

Update: Small bug fixes, such as access to federated sources, multi-connect feature, and desktop shortcut problems. (Details are available in the change history installed with the software.)


9 comments | Printer Friendly Page  Send to a Friend | Score: 0
Posted by Anonymous on Sunday, January 11, 2004 (00:00:00) (2389 reads)

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