Reducing Client Connection Delays When DNS Is Unresponsive
Last updated on MAY 17, 2018
Applies to:Oracle Net Services - Version 188.8.131.52 to 184.108.40.206 [Release 11.2 to 12.1]
JDBC - Version 220.127.116.11.0 to 18.104.22.168.0 [Release 11.2]
Oracle Net Services - Version 22.214.171.124 to 126.96.36.199 [Release 11.2]
Oracle Database - Enterprise Edition - Version 188.8.131.52 to 184.108.40.206 [Release 11.2]
Oracle Database - Enterprise Edition - Version 220.127.116.11 to 18.104.22.168 [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
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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