# Background Task Management Overview

On an OS that allows for user interaction, resources gravitate to service processes that interact with users. In other words, apart from processes that support system running, service processes that can be perceived by users have the highest priority. Therefore, background task management is applicable to service processes that cannot be perceived by users.


## Background Task Types

Background tasks described in this document refer to the services that need to be continued when the respective applications or service modules are running in the background (not visible to the users). For more targeted management of background applications and service modules, OpenHarmony classifies applications and service modules into the following types:

1. No background task: An application or service module does not need further processing when switched to the background.

2. Transient task: If an application or service module has an urgent, short task that must continue in the background until it is completed, such as data compression, the application or service module can request a transient task for delayed suspension.

3. Continuous task: If an application or service module has a user-initiated, perceivable task that needs to run in an extended period of time in the background, it can request a continuous task so that it will not be suspended. Examples of continuous tasks include music playback, navigation, upload and download, device connection, and VoIP.


## Transient Tasks

As mentioned above, applications and service modules with transient tasks have their suspension delayed so that their running is not affected by background lifecycle management within the specified time frame.

> ![icon-note.gif](public_sys-resources/icon-note.gif) **Note:**
> Applications and service modules can request transient tasks only for temporary tasks. The time quota is 3 minutes per time and 10 minutes per day. The system allocates the time frame based on the application scenario and system status.


### Restrictions on Using Transient Tasks

Adhere to the following constraints and rules when using transient tasks:

- **When to request**: An application can request a transient task only when it is running in the foreground or before it is suspended in the background. Otherwise, the application may be suspended, resulting in request failure. By default, an application has 6–12 seconds of running time (subject to the application scenario) before it is suspended in the background.

- **Timeout**: The system notifies the application of the suspension delay timeout by using a callback. The application must then cancel the delayed suspension or apply for delayed suspension again. Otherwise, the application will be forcibly suspended.

- **When to cancel**: The requesting application shall cancel the request when the transient task is complete. If the request is forcibly canceled by the system, the time frame allowed for the application to run in the background will be affected.

- **Quota mechanism**: To prevent abuse of the keepalive, each application has a certain quota every day (dynamically adjusted based on user habits). After using up the quota, an application cannot request transient tasks. Therefore, applications should cancel their request immediately after the transient tasks are complete, to avoid quota consumption. (Note: The quota refers to the requested duration and does not include the time when the application runs in the background.)