IAC iview is used when you want to create an iview of an ITS service. In the thrid step of creating IAC iview we should pass the ITS service name for IAC property.
Steps to create IAC iview.
1. Create a system object for R/3 with ITS property category also.
2. create a Service in transaction using SICF. The below thread will help you.

https://www.sdn.sap.com/irj/sdn/weblogs?blog=/pub/wlg/2204
3. create an an iview and give the service name in IAC textbox not R/3 System name.

Also check:
https://www.sdn.sap.com/irj/sdn/thread?threadID=243082

http://help.sap.com/saphelp_nw04/helpdata/en/44/216fe21784648ee10000000a1553f7/frameset.htm

M again mentioning all the steps for IAC iview creation, plz check.

Steps to display the SAP Transaction as Internet Application Component (IAC) in Portal
The following three tasks have to be performed step by step:
1.Creating the IAC
2.Activating the IAC
3.Creating an IAC iview in the portal

Creating an IAC
1)Go to transaction sicf. Click on the "watch"button. Under Virtual Host / Services expand Default_host > SAP > bc > gui > sap > ITS. Now right click over ITS and select New Sub-Element.
2)In the new dialog box give the name of the service.
3)Now write a description in the description box. In the drop box corresponding to GUI Link select the option Yes. Now click the GUI Transaction button and enter the parameters as shown below.
Parameter Name Value
~TRANSACTION sm36
~THEME 99
~generateDynpro 1
~noHeaderOkCode 1
4)Now go to the tab Handler List and maintain the parameter CL_HTTP_EXT_ITS.
Now click on the save button from the top and save it.
You can now see the service under ITS.

Activating the service

After saving the IAC, we need to activate the service. Select the service under ITS, right click over it and select Activate Service. The service will get activated.

Creating an IAC iview in the portal

We need to create an iview which in tern will use a system to connect to the ITS.
In the WAS property of the system maintain the following property
Web As Host Name :
Web As Path /sap/bc/gui/sap/its/
Web As Protocol HTTP/HTTPS
Under Content Administration > Portal Content create an iview of type SAP IAC iview and specify the system alias name and the IAC.

source
http://forums.sdn.sap.com/thread.jspa?threadID=841234