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

Last updated on SEPTEMBER 20, 2023

Applies to:

Oracle Net Services - Version and later
JDBC - Version to [Release 11.1 to 11.2]
Oracle Database - Enterprise Edition - Version to [Release 19]
Information in this document applies to any platform.


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 the client and the database are on different networks, and the 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



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


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