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Mysterious Issue – Oracle 19c (19.17) Stopped Accepting New Connections

edited Jun 21, 2025 9:52PM in Database Administration (MOSC) 6 commentsAnswered

Mysteriously, the Oracle 19c database (19.17 Release Update) stopped accepting new connections around 02:00 AM on 05/22/2025.

The database was in OPEN mode. Below is a screenshot of a query executed on the database:

The listener was operational (see screenshot below):

There were no connectivity issues, as we tested with telnet on the default database port, and everything was working correctly.

However, when a remote application attempted to connect to the database, it would simply hang indefinitely, waiting for a session. We tested with multiple applications written in different languages (Java/JDBC, Python oracledb, PHP OCI, etc.), and the behavior was the same.

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