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

Last updated on JULY 06, 2021

Applies to:

Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Oracle Database Cloud Service - Version N/A and later
JDBC - Version to [Release 11.2 to 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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