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# Como resolver o erro "Failed to initialize pool: ONS configuration failed"

Saiba como solucionar o erro que impede uma aplicação Java de se conectar a um banco de dados Oracle.

Ao tentar estabelecer a conexão entre uma aplicação Java e um banco de dados Oracle, pode aparecer a seguinte mensagem de erro:

{% code overflow="wrap" %}

```
"Could not establish connection to the database. Error com.zaxxer.hikari.pool.HikariPool$PoolInitializationException: Failed to initialize pool: ONS configuration failed"
```

{% endcode %}

## **Identificando a causa do erro**

Este erro geralmente ocorre devido a configurações incorretas no Oracle Notification Service (ONS). O ONS é responsável por notificar a aplicação sobre alterações no banco de dados. No entanto, uma configuração inadequada pode interromper a conectividade e causar esse problema.

## **Corrigindo o erro**

Para resolver esse erro, é necessário desabilitar o ONS adicionando um parâmetro à configuração do seu conector. Siga os passos abaixo:

1. Abra a configuração do conector de banco de dados (geralmente, o conector [**DB**](/documentation/connectors-and-triggers/pt-br/connectors/structured-data/db-v2.md) é utilizado nesses casos).
2. Localize o parâmetro que define a configuração do banco de dados Oracle.
3. Adicione a seguinte linha para desabilitar o ONS: `"oracle.jdbc.fanEnabled" : false`

<figure><img src="https://content.gitbook.com/content/3ANg0NQQeslB7Og5K7Ah/blobs/I4dv2d1ZU6GQDwWXgYC1/image1.png" alt=""><figcaption><p>Exemplo de configuração.</p></figcaption></figure>

4. Salve o conector e teste a execução.

Se a configuração estiver correta, a conexão com o banco de dados deve ser bem sucedida.


---

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