add FAN FAQ (#1296)

* add FAN FAQ

* edit title

* fix one minor typo

* incorporate reviewer comments

* fix date and adjust the awkward sentence

Author: rosemarymarano

docs-source/content/faq/fan.md

@@ -0,0 +1,67 @@
+---
+title: "Disabling Fast Application Notifications"
+date: 2019-10-11T17:20:00-05:00
+draft: false
+---
+
+To support Fast Application Notifications (FAN), Oracle databases configure GRID (Oracle Grid Infrastructure).
+GRID is typically associated with (and required by) Oracle RAC databases but can
+also be used in other configurations.  Oracle Autonomous Database-Serverless (ATP-S) does not provide GRID.
+
+When connecting to a database that does not have GRID, the only type of WebLogic Server
+data source that is supported is the Generic Data Sources. Multi Data Sources and Active GridLink
+data sources cannot be used because they work with RAC.
+
+
+WebLogic Server 12.2.1.3.0 shipped with the 12.2.0.1 Oracle driver. When connecting
+with this driver to a database that does not have GRID, you will
+encounter the following exception (however, the 18.3 driver does not have this problem):
+
+```
+oracle.simplefan.impl.FanManager configure
+SEVERE: attempt to configure ONS in FanManager failed with oracle.ons.NoServersAvailable: Subscription time out
+```
+
+To correct the problem, you must disable FAN, in one of two places:
+
+1)	Through a system property at the domain, cluster, or server level.  
+
+To do this, edit the Domain Custom Resource to set the system property `oracle.jdbc.fanEnabled`
+to `false` as shown in the following example:
+
+```
+  serverPod:
+    # an (optional) list of environment variable to be set on the servers
+    env:
+    - name: JAVA_OPTIONS
+      value: "-Dweblogic.StdoutDebugEnabled=false -Doracle.jdbc.fanEnabled=false"
+```
+
+2) Configure the data source connection pool properties.  
+
+The following WLST script adds the
+ `oracle.jdbc.fanEnabled` property, set to `false`, to an existing data source.
+
+```
+       fmwDb = 'jdbc:oracle:thin:@' + db
+       print 'fmwDatabase  ' + fmwDb
+       cd('/JDBCSystemResource/LocalSvcTblDataSource/JdbcResource/LocalSvcTblDataSource')
+       cd('JDBCDriverParams/NO_NAME_0')
+       set('DriverName', 'oracle.jdbc.OracleDriver')
+       set('URL', fmwDb)
+       set('PasswordEncrypted', dbPassword)
+
+       stbUser = dbPrefix + '_STB'
+       cd('Properties/NO_NAME_0/Property/user')
+       set('Value', stbUser)
+       ls()
+       cd('../..')
+       ls()
+       create('oracle.jdbc.fanEnabled','Property')
+       ls()
+       cd('Property/oracle.jdbc.fanEnabled')
+       set('Value', 'false')
+       ls()
+```
+After changing the data source connection pool configuration, for the attribute to take effect,
+make sure to undeploy and redeploy the data source, or restart WebLogic Server.