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Intermittent TNS-12521 and ORA-12514 On RAC With DataGuard (Doc ID 2546305.1)

Last updated on AUGUST 09, 2023

Applies to:

Universal Connection Pool - Version and later
Information in this document applies to any platform.


JDBC application using JDBC/thin and UCP fails to connect with error ORA-12514  TNS:listener does not currently know of service requested in connect descriptor
when connecting to a DataGuard (DG) where the primary is the second address.

This issue occurs when trying to connect to DG standby. Also, this issue occurs only when DG is added to the JDBC URL.

TNS-12521 TNS:listener does not currently know of instance requested in connect descriptor errors are regularly seen in the listener logs. However, the connections can still succeed when there is no DG.
But, when the DG is added, connections fail with ORA-12514.

Exception stack

ORA-12514, TNS:listener does not currently know of service requested in connect descriptor
at oracle.jdbc.driver.T4CConnection.connect(
at oracle.jdbc.driver.T4CConnection.logon(


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