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<concept id="GUID-0371FD21-D988-4560-891F-2840C36AB2E2" xml:lang="en"><title>Out

of Memory Error</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>An Out of Memory (OOM) error occurs if an application allocates large amount

of RAM in too short time. In such situations, the free RAM level drops as

the application allocates RAM faster than the OOM Monitor can release RAM

from other applications.</p>

<p>To avoid this OOM Monitor has the <codeph>KOomMaxAllocationWithoutPermission</codeph> constant.

It defines the maximum amount of RAM that an application can safely allocate

within two seconds without OOM Monitor's permission.</p>

<p> The <codeph>KOomMaxAllocationWithoutPermission</codeph> value defined

in the OOM Monitor header file cannot not be modified. The RAM can be allocated

quickly in small pieces as long as the total amount of allocated RAM within

two seconds is less than <codeph>KOomMaxAllocationWithoutPermission</codeph>. </p>

<p>If an application needs to allocate more RAM than <codeph>KOomMaxAllocationWithoutPermission</codeph> value,

it must request permission from the OOM Monitor. OOM Monitor provides two

different methods for this purpose. <ul>

<li><p><xref href="GUID-02D1911A-D2E5-3D28-9B05-75DA0A75DE73.dita#GUID-02D1911A-D2E5-3D28-9B05-75DA0A75DE73/GUID-BE322080-5193-3D8E-9425-C6BEA920ED2E"><apiname>ROomMonitorSession::RequestFreeMemory()</apiname></xref> is used

for mandatory RAM allocation. For more information, refer to <xref href="GUID-50CA5439-29A1-426C-83BA-EC048FE86CDE.dita">Allowing

Large Memory Allocation</xref>.</p></li>

<li><p><xref href="GUID-02D1911A-D2E5-3D28-9B05-75DA0A75DE73.dita#GUID-02D1911A-D2E5-3D28-9B05-75DA0A75DE73/GUID-D0AD593E-3C07-34B5-B8A2-24AABA42AFD7"><apiname>ROomMonitorSession::RequestOptionalRam()</apiname></xref> is used

for optional RAM allocation. For more information, refer to <xref href="GUID-217C992B-AC56-42A7-9920-DEC891D233A5.dita">Allowing

Optional RAM Allocation</xref>.</p></li>

</ul> OOM error can still occur in the following situations:</p>

<ul>

<li><p>An application allocates more than <codeph>KOomMaxAllocationWithoutPermission</codeph> amount

of RAM within two seconds without OOM Monitor's permission. And the OOM Monitor

cannot release the RAM fast enough for the application.</p></li>

<li><p>An application allocates less than <codeph>KOomMaxAllocationWithoutPermission</codeph> amount

of RAM within two seconds but </p><ul>

<li><p>some applications do not release RAM quickly enough when requested

(OR)</p></li>

<li><p>several applications allocate RAM at the same time.</p></li>

</ul></li>

</ul>

<p>Therefore it is important that all applications are prepared to handle

OOM errors. </p>

<section id="GUID-77B379F3-1ECA-4C62-A9C9-720C8882ED43"><title>Closing an

application on the OOM Monitor request</title><p>To avoid an OOM error, applications

must terminate itself without any delay whenever the OOM Monitor requests

so. Otherwise the time of free RAM amount below <keyword>LOW_RAM_THRESHOLD</keyword> gets

longer and another application can allocate RAM during that time resulting

in an OOM error.</p><p>Applications when closed by the OOM Monitor receives <codeph>EEikCmdExit</codeph> event.</p></section>

</conbody></concept>