Runtime Client-Server Domains (Reference)

Domain Concepts

Server Domain

• Scope: Global across all modules and clients
• Process: TServer.exe
• Contains: Device communications, alarms, historian, server scripts
• Tag Access: Server tags only
• Use For: PLC data, shared values, system-wide calculations

Client Domain

• Scope: Local to each client computer
• Process: Client.exe (Rich/Smart/Web)
• Contains: Displays, client scripts, local variables
• Tag Access: Both server and client tags
• Use For: Operator input, display parameters, local calculations

Namespace Architecture

Tag Domain Configuration

Server Tags (Default)

Characteristics:

• Same value across all clients
• Synchronized automatically
• Stored in server memory

Use Cases:

• PLC/device data
• Process variables
• Alarm triggers
• Historian points
• Shared calculations

Client Tags

Characteristics:

• Local to each client
• Not synchronized
• Client memory only

Use Cases:

• Operator input fields
• Display navigation
• Report parameters
• Local calculations
• UI state variables

Module Domain Behavior

Dataset Operations

Synchronous Execution

csharp

// Executes where called (client or server)
@Dataset.Table.Table1.SelectCommand()

• Runs in calling domain
• Immediate execution
• Blocks until complete

Asynchronous Execution

csharp

// Always executes on server
@Dataset.Table.Table1.Select += 1

• Server-side only
• Non-blocking
• Fire-and-forget

Important: When using client tags in SQL queries or mappings, use synchronous methods from client domain.

Report Operations

Similar to datasets, reports support both synchronous and asynchronous execution:

Files always save on the server, regardless of where the command originated.

Script Execution

Server Scripts

• Run in TServer.exe process or separate AppDomain
• Access server tags only
• Can be distributed to remote computers
• Protected execution environment

Client Scripts

• Run in client process threads
• Access both server and client tags
• Local to each client
• UI interaction capable

Calling Server Methods from Client

When calling server methods from client scripts, use async/await:

C#:

csharp

public async Task DisplayOpening()
{
    await @Script.Class.ServerMain.Method1();
}

VB.NET:

vbnet

Public Async Function DisplayOpening() As Task
    Await @Script.Class.ServerMain.Method1()
End Function

Built-in Protections

Script Safety

• Automatic try-catch wrapping
• Reentrancy prevention
• Task queue management
• Thread pool optimization
• Real-time data synchronization

Performance

• Separate execution threads per task
• CPU core-based thread pooling
• Non-blocking architecture
• Automatic load balancing

Best Practices

Domain Selection

1. Use Server Domain for:
   • Shared data across clients
   • Device communications
   • System-wide calculations
   • Historical data
2. Use Client Domain for:
   • User interface state
   • Local preferences
   • Temporary calculations
   • Display parameters

Performance Optimization

• Minimize client-server tag synchronization
• Use appropriate domain for calculations
• Batch database operations
• Cache frequently accessed server data locally

Security Considerations

• Server process has database credentials
• Clients access data through server
• No direct database access from clients
• Domain separation ensures data isolation