> For the complete documentation index, see [llms.txt](https://docs.novacura.com/flow-connect/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.novacura.com/flow-connect/working-with-connect/connect-to-systems/connectors/opc-ua/additional-property-string.md).

# Additional Property String

The `Additional Property String` field accepts an XML configuration block as shown below to fine-tune the OPC UA client behavior with some additional properties.

```
<?xml version="1.0" encoding="utf-8"?>
<OpcUaAdvancedConfiguration>
    <Application>
        <ProductUri></ProductUri>
        <DisableHighResolutionClock>false</DisableHighResolutionClock>
    </Application>
    <TransportQuotas>
        <OperationTimeout>120000</OperationTimeout>
        <MaxStringLength>65535</MaxStringLength>
        <MaxByteStringLength>1048560</MaxByteStringLength>
        <MaxArrayLength>65535</MaxArrayLength>
        <MaxMessageSize>2097152</MaxMessageSize>
        <MaxBufferSize>65535</MaxBufferSize>
        <ChannelLifetime>30000</ChannelLifetime>
        <SecurityTokenLifetime>3600000</SecurityTokenLifetime>
    </TransportQuotas>
    <ClientConfiguration>
        <DefaultSessionTimeout>60000</DefaultSessionTimeout>
        <EndpointCacheFilePath></EndpointCacheFilePath>
        <MinSubscriptionLifetime>10000</MinSubscriptionLifetime>
    </ClientConfiguration>
    <SecurityAdvanced>
        <SendCertificateChain>true</SendCertificateChain>
        <AddAppCertificateToTrustedStore>true</AddAppCertificateToTrustedStore>
        <MinCertificateKeySize>2048</MinCertificateKeySize>
        <RejectSHA1SignedCertificates>true</RejectSHA1SignedCertificates>
        <AutoAcceptUntrustedCertificates>true</AutoAcceptUntrustedCertificates>
        <NonceLength>32</NonceLength>
    </SecurityAdvanced>
    <CertificateStores>
        <TrustedUserCertificates>
            <StorePath></StorePath>
        </TrustedUserCertificates>
        <UserIssuerCertificates>
            <StorePath></StorePath>
        </UserIssuerCertificates>
        <HttpsIssuerCertificates>
            <StorePath></StorePath>
        </HttpsIssuerCertificates>
        <TrustedHttpsCertificates>
            <StorePath></StorePath>
        </TrustedHttpsCertificates>
    </CertificateStores>
    <SessionAdvanced>
        <OperationTimeout>5000</OperationTimeout>
        <SessionName></SessionName>
        <SessionTimeout>1800000</SessionTimeout>
        <UpdateBeforeConnect>false</UpdateBeforeConnect>
    </SessionAdvanced>
</OpcUaAdvancedConfiguration>
```

This section provides a detailed explanation of the available sections and properties.

#### Application <a href="#user-content-application" id="user-content-application"></a>

| Property                       | Type    | Default   | Description                                                                                                                   |
| ------------------------------ | ------- | --------- | ----------------------------------------------------------------------------------------------------------------------------- |
| **ProductUri**                 | text    | *(empty)* | The product URI identifying this OPC UA client application in the server's session list.                                      |
| **DisableHighResolutionClock** | boolean | `false`   | When `true`, disables the high-resolution clock for timestamps. Use on systems where the high-resolution timer is unreliable. |

#### TransportQuotas <a href="#user-content-transportquotas" id="user-content-transportquotas"></a>

| Property                  | Type           | Default   | Description                                                                                          |
| ------------------------- | -------------- | --------- | ---------------------------------------------------------------------------------------------------- |
| **OperationTimeout**      | number (ms)    | `120000`  | Maximum time in milliseconds to wait for a transport-level operation to complete before timing out.  |
| **MaxStringLength**       | number         | `65535`   | Maximum length of a string value that can be sent or received in a single message.                   |
| **MaxByteStringLength**   | number         | `1048560` | Maximum length of a byte string (binary data) that can be sent or received.                          |
| **MaxArrayLength**        | number         | `65535`   | Maximum number of elements allowed in an array value.                                                |
| **MaxMessageSize**        | number (bytes) | `2097152` | Maximum size of a single OPC UA message in bytes (2 MB default).                                     |
| **MaxBufferSize**         | number (bytes) | `65535`   | Maximum size of the send/receive buffer for a single message chunk.                                  |
| **ChannelLifetime**       | number (ms)    | `30000`   | Lifetime of the secure channel in milliseconds before it must be renewed.                            |
| **SecurityTokenLifetime** | number (ms)    | `3600000` | Lifetime of the security token in milliseconds (1 hour default). The token is renewed before expiry. |

#### ClientConfiguration <a href="#user-content-clientconfiguration" id="user-content-clientconfiguration"></a>

| Property                    | Type        | Default   | Description                                                                                                |
| --------------------------- | ----------- | --------- | ---------------------------------------------------------------------------------------------------------- |
| **DefaultSessionTimeout**   | number (ms) | `60000`   | Default session timeout requested from the server. The server may revise this value.                       |
| **EndpointCacheFilePath**   | text        | *(empty)* | File path where discovered endpoint descriptions are cached locally. Leave empty to disable caching.       |
| **MinSubscriptionLifetime** | number (ms) | `10000`   | Minimum lifetime for subscriptions. The client will not request a subscription lifetime shorter than this. |

#### SecurityAdvanced <a href="#user-content-securityadvanced" id="user-content-securityadvanced"></a>

| Property                            | Type           | Default | Description                                                                                                                                               |
| ----------------------------------- | -------------- | ------- | --------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **SendCertificateChain**            | boolean        | `true`  | When `true`, sends the full certificate chain (including CA certificates) during the secure channel handshake.                                            |
| **AddAppCertificateToTrustedStore** | boolean        | `true`  | When `true`, automatically adds the application's own certificate to the trusted store on startup.                                                        |
| **MinCertificateKeySize**           | number (bits)  | `2048`  | Minimum RSA key size accepted for peer certificates. Certificates with smaller keys are rejected.                                                         |
| **RejectSHA1SignedCertificates**    | boolean        | `true`  | When `true`, rejects certificates signed with the SHA-1 algorithm (considered insecure).                                                                  |
| **AutoAcceptUntrustedCertificates** | boolean        | `true`  | When `true`, automatically accepts untrusted server certificates without manual approval. Set to `false` in production for strict certificate validation. |
| **NonceLength**                     | number (bytes) | `32`    | Length of the cryptographic nonce used during secure channel creation.                                                                                    |

#### CertificateStores <a href="#user-content-certificatestores" id="user-content-certificatestores"></a>

| Property                               | Type | Default   | Description                                                                                       |
| -------------------------------------- | ---- | --------- | ------------------------------------------------------------------------------------------------- |
| **TrustedUserCertificates.StorePath**  | text | *(empty)* | Path to the certificate store containing trusted user certificates for user-level authentication. |
| **UserIssuerCertificates.StorePath**   | text | *(empty)* | Path to the certificate store containing CA certificates that issued trusted user certificates.   |
| **HttpsIssuerCertificates.StorePath**  | text | *(empty)* | Path to the certificate store containing CA certificates for HTTPS transport validation.          |
| **TrustedHttpsCertificates.StorePath** | text | *(empty)* | Path to the certificate store containing trusted HTTPS certificates for transport-level security. |

#### SessionAdvanced <a href="#user-content-sessionadvanced" id="user-content-sessionadvanced"></a>

| Property                | Type        | Default   | Description                                                                                                                             |
| ----------------------- | ----------- | --------- | --------------------------------------------------------------------------------------------------------------------------------------- |
| **OperationTimeout**    | number (ms) | `5000`    | Maximum time in milliseconds to wait for a session-level service call (Read, Write, Browse) to complete.                                |
| **SessionName**         | text        | *(empty)* | Custom name for the session as displayed in the server's session diagnostics. If empty, a default name is generated.                    |
| **SessionTimeout**      | number (ms) | `1800000` | Requested session timeout in milliseconds (30 minutes default). The server closes the session if no activity occurs within this period. |
| **UpdateBeforeConnect** | boolean     | `false`   | When `true`, fetches the latest server endpoints from the discovery service before establishing the session.                            |


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.novacura.com/flow-connect/working-with-connect/connect-to-systems/connectors/opc-ua/additional-property-string.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.