Oracle.ManagedDataAccess OracleInternal.NotificationServices.ONSException

Question

We use the 'Oracle.ManagedDataAccess' ODP.NET driver for database access to Oracle.

When connecting to the database with the connection string:

Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(Host=10.40.40.38)(Port=1521)))(CONNECT_DATA=(SERVICE_NAME=D3T))); User Id=test; Password=test'

Internal error message:

OracleInternal.NotificationServices.ONSException**: ONS: No node lists have been configured' after opening the connection.

code:

string connect = "Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(Host=10.40.40.38)(Port=1521)))(CONNECT_DATA=(SERVICE_NAME=D3T))); User Id=test; Password=test";
OracleConnection connection = new OracleConnection(connect);
connection.Open();

The connection to the database is working fine. But what is internally wrong with the configuration?

The ONS service is not started or configured on the Oracle server. Why do I get this error? — J. Deing
– J. Deing, Commented Jan 10, 2018 at 9:54
The ons. config on the server has the following content: localport=6150 remoteport=6250 nodes=10.40.40.38:6250 But the ONS service (onsctl) is not started. — J. Deing
– J. Deing, Commented Jan 10, 2018 at 9:57
I get this after switching from Devart to the Oracle .NET Core 2 beta driver. — Kody
– Kody, Commented Jun 4, 2018 at 20:14
I have the same issue when I starting my application. I get 'OracleInternal.NotificationServices.ONSException' in Oracle.ManagedDataAccess.dll six times when I openning the connection. — honzakuzel1989
– honzakuzel1989, Commented Sep 4, 2018 at 8:25

Jacob Peterson · Accepted Answer · 2019-07-12 16:36:57Z

8

I found this link helpful: https://www.databaseusers.com/article/6046913/ONS%3A+No+node+lists+were+configured

Basically, you need to configure ONS, or disable LoadBalancing and HAEvents like so:

Oracle.ManagedDataAccess.Client.OracleConfiguration.LoadBalancing = false;
Oracle.ManagedDataAccess.Client.OracleConfiguration.HAEvents = false;

answered Jul 12, 2019 at 16:36

Jacob Peterson

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Comments

WarpEnterprises · Accepted Answer · 2020-09-25 16:24:13Z

6

We configure the OracleConnection with a single connection string (without any xml).
Setting those two parameters is possible using the following names, the other parts are for example and not relevant for this problem.

Data Source=(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=mydbhost)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=myservicename)));load balancing=false;ha events=false;Min Pool Size=1;Incr Pool Size=1;user id=mydbuser

answered Sep 25, 2020 at 16:24

WarpEnterprises

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sandeepdhankar10 · Accepted Answer · 2020-01-04 06:45:12Z

5

Thanks to Jacob Peterson.

But if you are unable to find the mentioned setting in C# code then configure your config as below. "Add settings if the block is already there"

<oracle.manageddataaccess.client>
    <version number="*">
      <settings>
        <setting name="LoadBalancing" value="false" />
        <setting name="HAEvents" value="false" />
      </settings>      
    </version>   
  </oracle.manageddataaccess.client>

answered Jan 4, 2020 at 6:45

sandeepdhankar10

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1 Comment

LuckyLuke82 Over a year ago

this eliminates error. But what does It mean anyway, I don't understand It at all ?

Marwan J. Al Khatib · Accepted Answer · 2021-01-11 17:37:49Z

2

I am using ODP.NET Managed Client for years and never saw those OSN exceptions until recent updates when migrating to .NET Core and using Oracle.ManagedDataAccess and Oracle.ManagedDataAccess.Core Nuget packages.

Thanks to Jacob Peterson and other members who suggested to either ignore or disable the both properties "LOAD BALANCING=False;HA Events=False". Each one generates 3 exceptions if enabled on opening connection.

I assume that the new releases suppose that those features are enabled regardless if the server and/or connection string were prepared for that.

So, I suggest to ignore them or append disabled values to the connection string.

answered Jan 11, 2021 at 17:37

Marwan J. Al Khatib

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Comments

Nishant Kumar · Accepted Answer · 2021-07-14 12:40:09Z

-1

I faced the same issue and fixed it if I add "load balancing=false;ha events=false" in my conn string.

answered Jul 14, 2021 at 12:40

Nishant Kumar

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1 Comment

Eric Aya Over a year ago

This is the same solution as in this other answer.

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