Process.SetQOSClass
-------------------

Sets the Quality Of Service class for the current thread.

| Component | Version | macOS | Windows | Linux | Server | iOS SDK |
|---|---|---|---|---|---|---|
| [Process](component_Process.md) | [16.1](newinversion161.md) | ✅ Yes | ✅ Yes | ✅ Yes | ✅ Yes | ✅ Yes |

MBS( "Process.SetQOSClass"; QOS ) 

**MBS**( **"Process.SetQOSClass";** /\* Sets the Quality Of Service class for the current thread. \*/  
**$QOS**) /\* The new QOS class.  
From highest level 5 down to background activity 1.e.g. 1 \*/ 

### Parameters

| Parameter | Description | Example |
|---|---|---|
| QOS | The new QOS class.   From highest level 5 down to background activity 1. | 1 |

### Result

Returns OK or error.

### Description

Sets the Quality Of Service class for the current thread.  
  
The Quality Of Service class for a thread tells the scheduler how to prioritize the thread and whether to run this on a faster or more efficient CPU core.  
  
MacOS can run threads marked as background on an efficient core to safe battery life.  
Linux does not allow to set higher priority (4 or 5) unless you have permissions to do so.  
  
Returns a native error code or OK in case of success.  
  
| Name | Value | Description |
|---|---|---|
| QOS\_CLASS\_USER\_INTERACTIVE | 5 | The thread handles user input. |
| QOS\_CLASS\_USER\_INITIATED | 4 | The user requested this action. |
| QOS\_CLASS\_DEFAULT | 3 | Default |
| QOS\_CLASS\_UTILITY | 2 | Utility thread running with reduced priority, e.g. menubar utility app. |
| QOS\_CLASS\_BACKGROUND | 1 | Background thread with reduced priority, e.g. backup. |
| QOS\_CLASS\_UNSPECIFIED | 0 | Unknown level. |

  
You may use this on the FileMaker server to mark long running scripts doing maintenance work as background thread, so they can run on efficient thread.  
### Examples

Set QOS to background:

 MBS ( "Process.SetQOSClass"; 1 )  
### See also

- [Process.GetQOSClass](ProcessGetQOSClass.md)

### Blog Entries

- [MBS FileMaker Plugin 16.1 News](https://www.mbsplugins.de/archive/2026-03-31/MBS_FileMaker_Plugin_161_News/monkeybreadsoftware_blog_filemaker)

This function checks for a license.

Created 8th March 2026 , last changed 4th May 2026

  
[Process.SetFrontMost](ProcessSetFrontMost.md) - [ProcessActivity.List](ProcessActivityList.md)

[HTML Version](ProcessSetQOSClass.shtml)