You connect the Informatica client to the repository server. You can access multiple Informatica repositories from a single client. You just keep adding repositories to your repository navigator. Each repository you add to the Informatica client includes a host name, a port number, and a repository name. The repository name must match the name stored in the repository database and the name specified during repository creation and restore. If you are mapping designer, adding repository to the client is probably the only setup you need to do.
The repository server can run in a different machine from the repository database. The repository server can be started without any repository information. You can configure the repository server in Informatica Repository setup tool. Not much to do actually since there are defaults already. You just need to enter a password, which you will use to connect to the repository server from the Repository Server Administration Console. The repository server itself is nothing but a process. you can run it from the control panel of the machine you want to start the repository. You need to create or load the repository to the repository databases to make the server useful.
Informatica Repository server communicate with repository database using the native drivers, so the machine you run the repository server must have the native driver installed. The machine you run your Informatica client does not need to have database connectivity for access the repository. In the case of access Oracle database, I think that you need to have SQL*Net installed.
You can create the repository or restore the repository remotely from Repository Server Administration Console (RSAC). RSAC is a client software, which access the repository server and perform the repository startup, restore, and repository server shutdown activities. You can create a new repository database or link the repository server to an existing repository database by specifying the database connection to the existing repository database.
If you are running Oracle BI Applications, Oracle provides the pre-packaged Informatica repository for the adapters for Oracle E-Business Suite, PeopleSoft, Siebel, and SAP. The Informatica repository database should be installed to the same database user who owns the DAC repository.
In Siebel Analytics 7.7, you can create the pre-packaged Informatica repository from DAC using Data Warehouse Configuration wizard. In Oracle BI Application 7.9, you should use the Informatica RSAC to restore the repository.
A repository server can manage multiple repository databases. You can see a list of repositories under each repsotory server in the RSAC. A repository database can only be started from a single repository server. If you configure a repository database from more then one repository server, you will get an error when you try to start the repository from the 2nd repository server.