> ## Documentation Index
> Fetch the complete documentation index at: https://docs.pads4.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Setup a SQL server failover

To ensure high availability and system redundancy, PADS4FIDS supports a **failover configuration** using two PADS4 servers with a shared SQL database and a DNS API switcher.

This setup ensures that if one PADS4 server becomes unavailable, the system can automatically redirect to the secondary server with minimal disruption.

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## Overview

* **SQL Database**: Hosted on a separate server (not on either PADS4 server)
* **Two PADS4FIDS Servers**: Installed on separate machines
* **DNS API Switcher**: Automatically redirects traffic between primary and secondary servers
* **Unified Access**: Viewers and operators use a common DNS address

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## Step-by-Step Setup

### Step 1: Prepare the SQL Database

* Set up a **SQL Server** on a dedicated machine in your network.
* Follow the standard steps for **creating a PADS4FIDS database** on this server.
* Ensure both PADS4 servers will have access to this SQL Server.

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### Step 2: Install Two PADS4FIDS Servers

* Deploy **two separate PADS4FIDS servers** (on two virtual or physical machines).
* These servers will **share the same licensing**, but you must contact the **PADS4 Sales Team** to authorize this configuration.
* Refer to the official **PADS4 installation manual** for setup instructions.

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### Step 3: Install a DNS API Switcher

* Install the **DNS API Switcher** on a machine that is **not one of the PADS4 servers**.
* This machine can be the SQL server or another system that can **communicate with both PADS4 servers and all PADS4 Viewers**.
* Configure the DNS API Switcher to:
  * Use the **primary PADS4 server** as the default endpoint
  * Automatically switch to the **secondary server** if the primary becomes unreachable

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### Step 4: Configure Viewers and Operator Access

* Configure all **PADS4 Viewers** to use the **DNS address** from the API switcher instead of a fixed server IP.

* The DNS address should be entered as the **PADS4 Server IP** in viewer connection settings.

* Default ports remain unchanged unless otherwise specified:
  * **Port 80** (HTTP)
  * **Port 7237** (PADS4 communication)

* Users accessing the **PADS4FIDS Operator** must also use the **DNS address** to ensure continuity, regardless of which server is active.

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## Network Diagram

*A network topology diagram would be displayed here, illustrating the relationship between:*

* SQL Server
* Primary and Secondary PADS4 Servers
* DNS API Switcher
* PADS4 Viewers and Operators