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<h1>OCI8 Fast Application Notification (FAN) Support</h1>
<div class="section">
<p class="para">
FAN support gives fast connection failover, an Oracle Database high availability
feature. This allows PHP OCI8 scripts to be notified when a
database machine or database instance becomes unavailable. Without
FAN, OCI8 can hang until a TCP timeout occurs and an error is
returned, which might be several minutes. Enabling FAN in OCI8 can
allow applications to detect errors and re-connect to an available
database instance without the web user being aware of an outage.
</p>
<p class="para">
FAN support is available when the Oracle client libraries that PHP
links with and the Oracle Database are either version 10gR2 or later.
</p>
<p class="para">
FAN benefits users of Oracle's clustering technology (RAC) because
connections to surviving database instances can be immediately
made. Users of Oracle's Data Guard with a broker will see the FAN
events generated when the standby database goes online. Standalone
databases will send FAN events when the database restarts.
</p>
<p class="para">
For active connections, when a machine or database instance becomes
unavailable, a connection failure error will be returned by the
OCI8 extension function currently being called. On a subsequent
PHP script re-connect, a connection to a surviving database
instance will be established. The OCI8 extension also
transparently cleans up any idle connections affected by a database
machine or instance failure so PHP connect calls will establish a
fresh connection without the script being aware of any service
disruption.
</p>
<p class="para">
When <a href="oci8.configuration.html#ini.oci8.events" class="link">oci8.events</a>
is <em>On</em>, it is suggested to
set <a href="oci8.configuration.html#ini.oci8.ping-interval" class="link">oci8.ping_interval</a>
to -1 to disable pinging, since enabling FAN events provide
pro-active connection management of idle connections made invalid
by a service disruption.
</p>
<p class="para">
To enable FAN support in PHP OCI8, build PHP OCI8 with Oracle 10gR2 or later
libraries and then follow these steps:
</p>
<p class="para">
<ul class="itemizedlist">
<li class="listitem">
<span class="simpara">
As a privileged database administrator, use a program like
SQL*Plus to enable the database service to post FAN events, for
example:
</span>
<p class="para">
<div class="informalexample">
<div class="example-contents screen">
<div class="cdata"><pre>
SQL> execute dbms_service.modify_service(
SERVICE_NAME => 'sales',
AQ_HA_NOTIFICATIONS => TRUE);
</pre></div>
</div>
</div>
</p>
</li>
<li class="listitem">
<span class="simpara">
Edit php.ini and add
</span>
<p class="para">
<div class="informalexample">
<div class="example-contents screen">
<div class="cdata"><pre>
oci8.events = On
</pre></div>
</div>
</div>
</p>
</li>
<li class="listitem">
<span class="simpara">
If the application does not already handle OCI8 error
conditions, modify it to detect failures and take appropriate
action. This may include re-connecting and re-executing
statements.
</span>
</li>
<li class="listitem">
<span class="simpara">
Run the application, connecting to Oracle Database 10gR2 or later.
</span>
</li>
</ul>
</p>
</div>
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