ora 24247 network access denied by access control list

2 min read 25-09-2024

ORA-24247: Network Access Denied by Access Control List: A Guide to Troubleshooting and Resolution

The dreaded ORA-24247 error, indicating "Network Access Denied by Access Control List," can be a frustrating hurdle for database administrators. It's often encountered when attempting to connect to an Oracle database from a remote client, indicating that your connection request has been blocked by the database's network security settings. This article will delve into the causes, troubleshooting steps, and effective solutions for this error.

Understanding the Problem

Oracle's network access control lists (ACLs) are a powerful security feature that enables you to precisely control which hosts and services can connect to your database. This level of granularity is crucial for protecting your sensitive data, but it can also lead to connectivity issues if configurations aren't carefully managed.

Causes of ORA-24247:

1. Incorrect or Missing ACL Entries: The most common reason for this error is a lack of an appropriate ACL entry permitting the connection from your specific client. This might be due to:

New Client Host: If you're connecting from a new host, the ACL might not have an entry for it yet.
Typographical Error: Mistakes in the hostname or IP address within the ACL entry can also prevent access.
Firewall Issues: Firewall rules might be blocking the connection even if an ACL entry exists.

2. Incorrect Listener Configuration: The Listener, a critical component responsible for accepting database connection requests, might have incorrect network configurations. Issues like incorrect port numbers or incorrect hostnames can lead to this error.

3. ACL Restrictions: The ACL itself might have limitations that prevent your connection. For example, you might only be allowed to connect through specific ports or protocols.

4. Privilege Issues: If your database user account lacks the necessary privileges to connect from the remote host, you'll encounter this error.

Troubleshooting ORA-24247:

Verify ACL Entries: Start by confirming the existence of the correct ACL entry for your client host. Use the following SQL statements:
```
SELECT * FROM DBA_NETWORK_ACLS; 
SELECT * FROM DBA_NETWORK_ACL_ENTRIES;
```
- Missing entry: If your client host is absent, create an entry using DBMS_NETWORK_ACL_ADMIN.CREATE_ACL.
- Incorrect entry: Update the existing entry using DBMS_NETWORK_ACL_ADMIN.UPDATE_ACL to correct any typos or configuration issues.
Check Listener Configuration: Review your Listener configuration for potential problems:
- Port Number: Ensure the Listener is listening on the correct port number for your client connection.
- Hostname: Ensure the hostname used in your listener configuration matches the hostname in your client connection string.
- Access Control: Verify that the Listener's access control settings aren't blocking the connection.
Firewall Rules: Double-check your firewall rules to ensure that the connection is not being blocked.
User Privileges: Confirm that your database user account has the necessary privileges to connect from your client host. You might need to grant the CONNECT role or the RESOURCE role for remote connections.

Example:

Suppose you want to allow connections from a client with IP address 192.168.1.10 to your database on port 1521. You would add the following ACL entry:

BEGIN
    DBMS_NETWORK_ACL_ADMIN.CREATE_ACL (
        acl => 'MY_ACL',
        description => 'Allow connections from client host',
        principal => '192.168.1.10',
        is_grant => TRUE,
        privilege => 'CONNECT',
        start_date => SYSDATE,
        end_date => NULL);
END;
/

Conclusion

The ORA-24247 error can be frustrating but can usually be resolved through careful analysis and troubleshooting. By understanding the causes, reviewing your ACL configurations, and verifying your Listener and firewall settings, you can regain control over your database connections and ensure smooth operations.

Remember: Always consult your database documentation and best practices for a comprehensive understanding of network security settings and best practices for managing your Oracle environment.

ora 24247 network access denied by access control list