All Oracle errors
ORA-12154net

TNS cannot resolve connect identifier

ORA-12154: TNS:could not resolve the connect identifier

Why it happens

The connection string in the app does not match any alias in tnsnames.ora, or the file is missing/pointing to the wrong TNS_ADMIN.

How to fix it

Confirm the tnsnames alias, the TNS_ADMIN environment variable, and case of the alias. Test with sqlplus user/pass@ALIAS on the same machine as the client.

A note on ORA-12154

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-12514 · Listener does not know of service

Build custom software with us

From internal tools to full platforms — we deliver end to end.

Start a Project
Was this tool useful?