For Smart P&ID, when working on an Oracle database, the Oracle client installation only is required. You install Oracle client after the Oracle database server installation has been completed. See Installing Oracle Database Server.
If one server hosts the databases of several products, Intergraph recommends that each product's database be a separate instance, each of which can host multiple plants.
The advantage of placing each product's database in its own instance is that only the affected application will be off-line during backup, performance tuning, and other database maintenance activities. Additionally, global tuning parameters that apply to one instance can be tailored to the specific product requirements.
According to Oracle documentation, the only limit to the number of instances you can have on any computer is the availability of resources. However, the number of instances on one database server should be minimized, because each additional instance places additional load on the server.
Each instance adds redundant tablespaces, rollback segments, background processes, and memory requirements for each SGA (System Global Area). For this reason, you should start by putting the database of one product for several plants into a single instance. Then, when the number of plants increases, or a plant becomes very large, consider separating the database into new instances, adding server memory, or even adding database servers.