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ORA-12543: TNS: destination host unreachable

What it means

The host cannot be reached on the network.

How to fix it

Check the host name, DNS, VPN and routing.

Catch it before it runs

ORA Error Helper
Explains ORA-/PLS- codes inside JetBrains IDEs and DataGrip.
PL/SQL Lint
Flags risky PL/SQL patterns while you type.
Oracle Plan Reader
Reads execution plans and points at the slow step.
PL/SQL in Practice
Kindle book with practical PL/SQL for working developers.

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Updated 2026-11-12.