All Oracle errors
TNS-12514net

Listener does not know the service

TNS-12514: TNS:listener does not currently know of service requested in connect descriptor

Why it happens

The listener is reachable but the requested service is not registered: wrong SERVICE_NAME/SID, the instance is down, or dynamic registration has not happened yet.

How to fix it

Check lsnrctl status for registered services, use the exact SERVICE_NAME from the database (not the SID), and start the instance or wait for PMON registration. Restart the listener after listener.ora changes.

A note on TNS-12514

This entry is part of a hand-curated set of ORA-, FRM-, REP- and TNS- codes that actually turn up in production Oracle estates — SQL*Plus, APEX, 19c/21c, ODP.NET apps, Oracle Forms 6i/12c and Reports included. The message text above is the canonical wording; the cause and fix are written in plain language so a developer or DBA can act without digging through pages of Oracle reference docs first.

Codes outside this list of 44 are far less common. If you hit one, the official Oracle error reference and your instance's alert or listener log remain the authoritative source.

Related net errors

ORA-03113 · End-of-file on communication channel ORA-03114 · Not connected to ORACLE ORA-12154 · TNS cannot resolve connect identifier

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