Oracle applications patching Maintenance mode: Why we need to put maintenance mode when applying patch in oracle applications:
While Applying a Patch, it is not Mandatory to Bring down All the Application Services except if it Mentioned in the Patch Read Me. The Scope of the Maintenance Mode is to Avoid the End users to log in to application at the time of... Patching.
As per the MOS Note 233044.1
Maintenance mode provides a clear separation between normal runtime operation of Oracle Applications
and system downtime for maintenance. Enabling the maintenance mode feature shuts down the Workflow
Business Events System and sets up function security so that no Oracle Applications functions are
available to users. Used only during AutoPatch sessions, maintenance mode ensures optimal performance
and reduces downtime when applying a patch. For more information, refer to Preparing your System for
Patching in Oracle Applications Maintenance Utilities.
"We are all apprentices in a craft where no one ever becomes a master."