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<concept id="GUID-3CDCE4E0-E29D-5782-8053-B386A9E34BCC" xml:lang="en"><title>Task

Scheduler Overview</title><abstract><p>The Task Scheduler enables clients to schedule tasks for time-based

and condition-based execution. The Task Scheduler is a <xref href="GUID-A3449F37-89BB-5208-8FD5-F4DF73F7E71A.dita">Startup

State Aware </xref> component. This ensures no task is initiated

before all system-level services are up and running. </p><p>The time or condition

for task execution is defined in a schedule. Schedules and tasks can be persistent

or transient. Schedules can be created, edited and deleted. </p><p> The Task

Scheduler participates in a system-wide backup or restore operation initiated

by the <xref href="GUID-EB624E33-0FB1-33BB-A423-0CB3C0A71548.dita"><apiname>Secure Backup Engine</apiname></xref> as a passive backup client.

This ensures the persistent schedules are backed up and restored.</p></abstract><prolog><metadata><keywords/></metadata></prolog><conbody>

<section><title>Required background</title> <p>In a condition-based schedule,

a condition can be user-defined or system condition. User defined conditions

are published using Publish and Subscribe keys. For more information about

Publish and Subscribe concept refer <xref href="GUID-A81C65CF-CF4E-571C-8080-9D387F46AAD6.dita"> Publish

and Subscribe.</xref>  </p> </section>

<section><title>Key concepts and terms</title> <dl>

<dlentry>

<dt>Task</dt>

<dd><p>The execution of an application or program. </p> </dd>

</dlentry>

<dlentry>

<dt> Schedule</dt>

<dd><p>A plan for performing a task. </p> </dd>

</dlentry>

<dlentry>

<dt>Persistent Schedule</dt>

<dd><p>The lifetime of a persistent schedule is not limited to the lifetime

of the tasks associated with it. </p> </dd>

</dlentry>

<dlentry>

<dt>Transient Schedule</dt>

<dd><p>A Transient schedule is created with a new scheduled task and is destroyed

on task destruction. Transient schedules and tasks are not persisted on disk-based

storage. </p> </dd>

</dlentry>

<dlentry>

<dt>Time-based Schedule</dt>

<dd><p>A Time-based schedule contains one or more tasks that are due for execution

at a specified time. </p> </dd>

</dlentry>

<dlentry>

<dt>Condition-based Schedule</dt>

<dd><p>A condition-based schedule contains one or more tasks which are executed

when either a set of certin Publish and Subscribe conditions are met or a

default time-out is reached. </p> </dd>

</dlentry>

<dlentry>

<dt> Home-Time based Schedule</dt>

<dd><p>A home-time based schedule occur at a given local time. Local time

typically includes changes for time zone and DST. These schedules are referred

to as ‘floating’ schedules. </p> </dd>

</dlentry>

<dlentry>

<dt>Daylight Saving Time (DST)</dt>

<dd><p>Daylight Saving Time (or summertime as it is called in many countries)

is a way of utilizing more daylight by advancing the local time by one hour

during the summer. </p> </dd>

</dlentry>

<dlentry>

<dt> Coordinated Universal Time (UTC) </dt>

<dd><p>UTC is independent of location. UTC-based schedules occur at a given

UTC time regardless of the local time. </p> </dd>

</dlentry>

</dl> </section>

<section><title>Architecture</title> <p>The task scheduler is a permanent

server. It is automatically started when the phone boots or reboots and does

not shutdown while the phone is running. If the server fails, and cannot be

automatically restarted, the phone restarts automatically. Persistent schedules

are stored the permanent file store. Transient schedules are lost if the server

fails. </p> <p>A client must register with the task scheduler before it can

schedule a task. </p> </section>

<section><title>APIs</title> <p>The main APIs of the task scheduler are: </p> <table id="GUID-827B6362-E8E1-5EA3-937F-E655CCEB97D2">

<tgroup cols="2"><colspec colname="col0"/><colspec colname="col1"/>

<thead>

<row>

<entry>API</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><p> <xref href="GUID-049FF2D7-8444-3E87-BF2F-DD0EA9B10ED0.dita"><apiname>CScheduledTask</apiname></xref>  </p> </entry>

<entry><p>A scheduled task </p> </entry>

</row>

<row>

<entry><p> <xref href="GUID-6E138B87-ED51-3C72-9075-8D7F887FA7B1.dita"><apiname>RScheduler</apiname></xref>  </p> </entry>

<entry><p>The client side interface to the Task Scheduler. </p> </entry>

</row>

</tbody>

</tgroup>

</table> </section>

<section><title>Typical uses</title> <p>The main uses of the task scheduler

are: </p> <ul>

<li id="GUID-5A6433D7-73AC-5FCA-AF14-60DFFBA69545"><p>Schedule a sequence

of tasks to be executed based on time. </p> </li>

<li id="GUID-F8F7BF9A-A42F-5C1F-A6E3-4DEA2202B4FE"><p>Schedule a sequence

of tasks to be executed based on conditions. </p> </li>

</ul> <p>For more information about using the task scheduler APIs, see the <xref href="GUID-74C1C345-823C-5CD5-8FC5-214A55734E94.dita">Developing Programs with

Task Scheduling Capabilities</xref> section. </p> </section>

<section><title>See also</title> <p><xref href="GUID-00363030-AAE2-5231-8407-AC609DA0F496.dita">Backup

and Restore on Scheduled Tasks in Persistent Schedules</xref>  </p> </section>

</conbody></concept>