If you have configured a failover cluster then obviously it will be taken care by the adjacent node which is online..
So, check for the failover config and if it is done it can be removed..
But still whatever you do better do it in an off working hours...
Why do you want to remove it only during work hours..?
That depends on whether you application can reply DMLs. If not transaction will be terminated and rolled back. I would wait till the transaction ended.
Transparent Application Failover (TAF) is a client-side feature that allows for clients to reconnect to surviving databases in the event of a failure of a database instance. Notifications are used by the server to trigger TAF callbacks on the client-side.
TAF is configured using either client-side specified TNS connect string or using server-side service attributes. However, if both methods are used to configure TAF, the server-side service attributes will supersede the client-side settings. The server-side service attributes are the preferred way to set up TAF.
TAF can operate in one of two modes, Session Failover and Select Failover. Session Failover will re-create lost connections and sessions. Select Failover will replay queries that were in progress.
When there is a failure, callback functions will be initiated on the client-side by means of OCI callbacks. This will work with standard OCI connections as well as Connection Pool and Session Pool connections. Please see the OCI manual for more details on callbacks, Connection Pools, and Session Pools.
TAF will work with RAC. For more details and recommended configurations, please see the RAC Administration Guide.
TAF will operate with Physical Data Guard to provide automatic failover."
When removing a node, you will first have to stop the instance(s) running on that node. If that node has current transactions, then you will kill those transactions unless TAF is in place and working correctly for your application.
This is one of the reasons why I insist on creating services. Don't rely on the service name that defaults to the database name. If you have set up a service, you can relocate that service to a remaining node. Over a period of time, the instance on this node won't have connections, at which time, you can shut it down.