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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>