Server scripts

Server scripts run on the server with no operator: counters, schedules, interlocks, sequences. They are started by tasks or from a screen through HMI.RunServerScript.

How they run

• All scripts and tasks run one at a time on a single thread, like a PLC scan, so they cannot race each other.
• Module globals last as long as the server runs. They start over after a restart or when a new project version is applied.
• Tag writes and system functions run in order after the script.
• Each run gets 5 seconds, 2,000,000 statements, recursion depth 256 and 64 MB of memory.
• The queue holds 10,000 runs. When it is full, new ones are dropped.

Standard JavaScript is available. setTimeout, fetch and require are undefined. For repetition, use an Interval task.

A script error does not stop the server: it is logged and queued writes are cancelled.

Tags

Member	Description
Tags(name).Name	Tag name
.Value	The value; null if quality is bad or there is no value
.Read()	Same as .Value
.Quality	Quality: Good, Uncertain, Bad, CommFailure, NoData and others
.Timestamp	Change time, ISO 8601, UTC
.Write(value)	Write after the script

Unlike on the client, .Value on the server is null after communication is lost. Allow for this in comparisons.

The Server object

Member	Description
Server.Now	Local server time as ISO text: 2026-11-09T15:30:00
Server.TextList(list, value)	Text from a text list
Server.SysFct(name, ...args)	A system function by name, after the script

The server runs tag and bit functions (except SetBitWhileKeyPressed and InputValue), calculations, AcknowledgeAllAlarms, AcknowledgeAlarm and RunScript. Window and screen functions do not work there, as the server has no windows.

Server.SysFct("IncreaseValue", "Counter", 1, 1000);
Server.SysFct("LinearScaling", "Tank1.Percent", "Tank1.Level", 0, 10, 0, 100);

Writes from server scripts are made under the user name Сервер.

Log

Method	Level
Log.Info(text), console.log(text)	Information
Log.Warn(text), console.warn(text)	Warning
Log.Error(text), console.error(text)	Error

Entries appear in the runtime window and in the files under %ProgramData%\Scadora\logs.

What started the script

The Trigger object describes what started the script.

Field	Description
Trigger.Task	Task name or kind of start
Trigger.Tag	The tag for Tag change and Condition tasks
Trigger.Value	New value
Trigger.Previous	Previous value
Trigger.User	The user, if called from a screen; otherwise Сервер

While a module loads, Trigger is null.

Calling from a screen

serverscripts/Main.js

function startSequence(recipe) {
  Log.Info(Trigger.User + " started recipe " + recipe);
  Tags("Seq.Recipe").Write(Number(recipe));
  Tags("Seq.Start").Write(true);
}

// a button script on a screen
HMI.RunServerScript("startSequence", "3");

The argument is always passed as text.

An on-screen table from a function

A Table element with a function source shows what the function returns: an array of arrays or an array of objects. In the second case, columns come from the first row’s properties.

function ordersTable() {
  return Db.Query("Journal", "SELECT Name, Qty FROM Orders");
}

Databases and files

var rows = Db.Query("Journal", "SELECT * FROM Events WHERE Id > ?", [100]);
rows.forEach(function (row) { Log.Info(row.Text); });

Method	Result
Db.Query(base, sql, params)	Array of objects: row.Name, row["Column name"]
Db.Execute(base, sql, params)	Number of changed rows
Db.Scalar(base, sql, params)	First value of the first row

Parameters replace ? and can be passed as an array or as arguments. Always use parameters rather than joining strings. Dates come back as ISO text and binary fields as Base64.

File access is covered in Tasks, databases, files.

Permissions

A server script reads and writes files with the server process’s rights, and absolute paths are allowed. The service runs as the system account, so only engineers should have write access to the production project folder.