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Reducing Client Connection Delays When DNS Is Unresponsive (Doc ID 1449843.1)

Last updated on AUGUST 04, 2018

Applies to:

Oracle Net Services - Version to [Release 11.2 to 12.1]
JDBC - Version to [Release 11.2]
Oracle Net Services - Version to [Release 11.2]
Oracle Database - Enterprise Edition - Version to [Release 11.2]
Oracle Database - Enterprise Edition - Version to [Release 12.1]
Information in this document applies to any platform.


In Oracle RAC clients frequently use DNS to resolve a scan name to one of three scan listener IP addresses.

Scan address setup in DNS

[mseibt@netbde]$ nslookup scan

In situations where the primary nameserver is down, to perform maintenance for example, client connectivity and any operation involving resolution of the scan name may experience a delay. The delay is at the OS level since the DNS query must timeout and then failover to the secondary or backup nameserver.

There are multiple areas that can be tuned to mitigate client connection delays when a nameserver is down. These tips and solutions are also helpful in non-RAC environments.


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