| CPU | 1 | CPU resources, which prevent the application from being suspended. |
| COMMON_EVENT | 2 | A type of software resources, which prevent common events from being proxied when the application is suspended. |
| TIMER | 4 | A type of software resources, which prevent timers from being proxied when the application is suspended. |
| WORK_SCHEDULER | 8 | WORK_SCHEDULER resources, which ensure that the application has more time to execute the task. |
| BLUETOOTH | 16 | A type of hardware resources, which prevent Bluetooth resources from being proxied when the application is suspended. |
| GPS | 32 | A type of hardware resources, which prevent GPS resources from being proxied when the application is suspended. |
| AUDIO | 64 | A type of hardware resources, which prevent audio resources from being proxied when the application is suspended.|
| COMMON_EVENT | 2 | Common events are not proxied when the application is suspended.|
| TIMER | 4 | System timers are not proxied when the application is suspended.|
| WORK_SCHEDULER | 8 | WorkScheduler uses a loose control policy by default. For details, see [Restrictions on Using Work Scheduler Tasks](../../task-management/background-task-overview.md#restrictions-on using-work-scheduler-tasks).|
| BLUETOOTH | 16 | Bluetooth resources are not proxied when the application is suspended.|
| GPS | 32 | GPS resources are not proxied when the application is suspended.|
| AUDIO | 64 | Audio resources are not proxied when the application is suspended.|
| RUNNING_LOCK | 128 | RUNNING_LOCK resources are not proxied when the application is suspended.|
| SENSOR | 256 | Sensor callbacks are not intercepted.|
Frequent activities of background applications cause user devices to consume power quickly and respond slowly. To meet performance and power consumption requirements, the system allows applications in the background to execute only activities within the specifications. Activities beyond the specifications are suspended by default, and resources allocated to them will be reclaimed when the available resources are insufficient.
If an application or a service module running in the background has a service to continue, it can request a [transient task](#transient-tasks) to delay the suspension or a [continuous task](#continuous-tasks) to prevent the suspension. If an application needs to execute a non-real-time task when running in the background, it can request a [Work Scheduler task](#work-scheduler-tasks). A privileged application can also request [efficiency resources](#efficiency-resources) for more flexibility.
**Resource usage constraints**: The system provides resource quotas for running services, including the memory usage and CPU usage in a continuous period of time, as well as disk write I/O volume in 24 hours. When the quota is reached, the system generates a warning-level log if the process is running in the foreground, and terminates the process if it is running in the background.
