Before installing Oracle Application Express, Oracle recommends that you complete the following steps:
Review and satisfy all Oracle Application Express installation requirements. See "Oracle Application Express Installation Requirements".
Shut down with normal or immediate priority the Oracle Database instances where you plan to install Oracle Application Express. On Oracle Real Application Clusters (Oracle RAC) systems, shut down all instances on each node.
An alternative to shutting down the database is to prevent all users from accessing Oracle Application Express when upgrading your installation from a previous release of Oracle Application Express. Oracle only recommends this option in high availability production environments where planned outages are not available. For all other scenarios, the database should be shut down.
To disable access to Oracle Application Express when the existing installation is using the Application Express Listener, shut down the appropriate application server where the Application Express listener is deployed.
To disable user access to Oracle Application Express when the existing installation is using the Oracle HTTP Server with mod_plsql, you should either shut down the Web server or disable the Application Express Database Access Descriptor of the Web server.
For an existing installation using the embedded PL/SQL gateway, you should disable the Oracle XML DB Protocol Server by setting the HTTP port to 0. This can be accomplished by starting SQL*Plus, connecting as SYS to the database where Oracle Application Express is installed, and running:
Once you have prevented access from Oracle Application Express users, you should log into SQL*Plus as SYS, connecting to the database where Oracle Application Express is installed, and query V$SESSION to ensure there are no long running sessions which would interfere with the upgrade process.
Back up the Oracle Database installation.
Oracle recommends that you create a backup of the current Oracle Database installation before you install Oracle Application Express. You can use Oracle Database Recovery Manager, which is included in the Oracle Database installation, to perform the backup.
Oracle Database Backup and Recovery User's Guide
Start the Oracle Database instance that contains the target database.
After backing up the system, you must start the Oracle instance that contains the target Oracle database. Do not start other processes such as a Web Listener. However, if you are performing a remote installation, make sure the database listener for the remote database has started.
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