EM Grid Control target discovery. How to add more targets after the agent is already there?

The article which explains it all:Metalink Note:239224.1

In short, the general points are:
1. There is a number of perl scripts in sysman/admin/discover directory, which are run by the agent configuration assistant at the end of agent installation.
2. Discover scripts search for all kinds of targets in all the known places (TNS_ADMIN, oratab, etc) and create the targets.xml file, which contains the list of discovered targets in xml format. file is saved into /sysman/emd directory.
3. If you need to add more targets after agent installation, you need to initiate the discovery process from within the grid control itself, by clicking "add" from the targets view.
4. As a last resort you could also try running the perl scripts manually, but this is not recommended.
5. Or even you can edit the targets.xml file and add targets manually and then run >emctl reload

Unsetting the instance parameters

Following syntax is used to unset a parameter:

SQL> alter system reset [parameter_name] scope=spfile sid='*';

where "sid" is the sid of the instance which needs to be affected in a RAC environment. In case of a single instance use "*".

What does it mean if SERVER = 'NONE' in v$session?

Definition:
SERVER  VARCHAR2(9)  Server type (DEDICATED| SHARED| PSEUDO| NONE)

From metalink:
In MTS/Shared Server configuration when you see value 'NONE' (as shown below), it means there is no task being processed by shared server for that session. The server column will infact show status of 'SHARED' if there is some task being processed at that particular time by the shared server process for that session.

In is also proved by the fact, that STATUS of session is always 'ACTIVE' for the sessions with 'SHARED' as value of SERVER and 'INACTIVE' for those with SERVER='NONE'.