JDBC Connections Using SCAN Fail With ORA-12516/ORA-12520 (Doc ID 1555793.1)

Last updated on JULY 31, 2017

Applies to:

JDBC - Version 11.1.0.6 to 11.2.0.4.0 [Release 11.1 to 11.2]
Oracle Net Services - Version 11.2.0.1 to 11.2.0.1 [Release 11.2]
Information in this document applies to any platform.

Symptoms

JDBC thin 11g connections using  Single Client Access Name (SCAN)  fail with errors:

ORA-12520: TNS:listener could not find available handler for requested type of server
ORA-12516: TNS : listener could not find instance with matching protocol stack

when client and database are on different networks and Network Address Translation (NAT) router is used for translation.
JDBC OCI and SQL*Plus connections work fine. JDBC connections using the HOST vip names work fine over the NAT router, only connections using SCAN fail. JDBC thin connections using SCAN without NAT router work without any problems

 

Changes

Network Devices like NAT, Load Balancers and usage of Domain Name Server (DNS) aliases for the SCAN name cause this failure.

Cause

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