FMW SOA 12.2.1.3 with the HA cluster installation questions

Products version FMW 12.2.1.3, SOA 12.2.1.3, OHS 12.2.1.3.

Hi everybody, I am planning this topology (figure 1-1) as oracle recommends high availability and documented main steps are:

1. Install Real Application Clusters Database
2. Install and configure middleware components
3. Install and configure Oracle HTTP Server
4. Configure a load balancer
5. Scale out the topology (machine scale out)Oracle Fusion MiddlewareOracle Fusion Middleware
6. Configure high availability for the Administration Server

There are what I did for that:

1. installed Data Tier, but in my case is not a RAC. (oracle database 12c, DBHOST)
2. installed Application tier. (FMW 12.2.1.3, SOA 12.2.1.3, APPHOST1)

next I should install Web tier(OHS), but I can’t understand how to install it. Whether install it in collocated with SOA domain or install it separately as standalone. According the guide “Installing and Configuring Oracle HTTP Server” it should be collocated with SOA domain. So if install it in collocated with SOA, then how to place it separate on the WEBHOST1 as the Figure 1-1 assumes?