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JDBC Connections Fail with ORA-12520 (Doc ID 2660207.1)

Last updated on FEBRUARY 26, 2024

Applies to:

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


Application using JDBC reports the following exception during connection to a database : Listener refused the connection with the following error:
ORA-12520, TNS:listener could not find available handler for requested type of server
  at oracle.jdbc.driver.T4CConnection.connect(
  at oracle.jdbc.driver.T4CConnection.logon(
  at oracle.jdbc.driver.PhysicalConnection.connect(
  at oracle.jdbc.driver.T4CDriverExtension.getConnection(
  at oracle.jdbc.driver.OracleDriver.connect(
  at java.sql.DriverManager.getConnection(

Also, TNS-12516 TNS:listener could not find instance with matching protocol stack may be reported.


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