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 11.2.0.1 and laterJDBC - Version 11.1.0.6 to 11.2.0.4.0 [Release 11.1 to 11.2]
Oracle Database - Enterprise Edition - Version 19.15.0.0.0 to 19.15.0.0.0 [Release 19]
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 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
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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In this Document
| Symptoms |
| Changes |
| Cause |
| Solution |
| References |