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Oracle

Oracle 19c - 23aiListener & Service

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ORA-12541: TNS:no listener / ORA-12514: TNS:listener does not currently know of service requested

Oracle Listener Inactive or Unknown Service: lsnrctl Diagnostics, Dynamic PMON Registration & Static Service Configuration

Troubleshooting inactive listener processes and service registration delays, enforcing instant dynamic registration with ALTER SYSTEM REGISTER and static listener fallback.

Reviewed by:Senior Database Architect & SRE (dataiotech Labs)

Tested Versions: Oracle Database 19c / 21c / 23ai

Operational Verification & Reliability Metadata

Last Technical Review: 2 Kasım 2026

Tested VersionsOracle 19c, 23ai

Required Privilegeslsnrctl access and ALTER SYSTEM privilege

Risk Assessment

HighStopped listener halts all inbound client connections across the instance

Expected Outputlsnrctl status reporting target service in READY status

Rollback Procedure:lsnrctl reload

Oracle Docs: Managing the Oracle Net Listener

First 60 Seconds Emergency Protocol:

The error string is a symptom, not the root cause. Do not restart the server blindly. Run the diagnostic queries below to pinpoint the actual failure mode.

▸Symptom

Clients encounter listener negotiation errors:

plaintext

ORA-12541: TNS:no listener
ORA-12514: TNS:listener does not currently know of service requested in connect descriptor

▸What You See in Production

•ORA-12541: No process is listening on target port 1521.
•ORA-12514: Listener is active, but target service has not registered.

▸Root Cause Matrix

Error	Probability	Root Cause
ORA-12541	%80	Listener daemon is stopped.
ORA-12514	%70	PMON/LREG dynamic registration has not broadcast yet.
ORA-12514	%30	Typo in requested `SERVICE_NAME`.

▸EMERGENCY RUNBOOK (0-5 min)

bash

# 1. Start listener daemon
lsnrctl start

sql

-- 2. Force immediate dynamic service registration
sqlplus / as sysdba
ALTER SYSTEM REGISTER;
SHOW PARAMETER service_names;

▸PERMANENT BLUEPRINT

1Static Service Registration: Add SID_LIST_LISTENER block to listener.ora.
2Configure LOCAL_LISTENER: Standardize registration parameters across RAC nodes.

▸Verification

bash

lsnrctl status

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