Installation
Ingres may be installed as a Client Installation or as a Server Installation, the difference being that the Client has no databases associated with it, but allows access to databases created in Server Installations.
A typical site would install Ingres Client Installations on its employees PCs, and these would communicate with the Ingres Server installations on the site's core computing facility.
Note that the expression "instance" is a synonym for "installation".
An installation can be viewed as a collection of server processes, shared memory and semaphores for interprocess communication, as well as disk-based files used for transaction processing and recovery in the event of a failure of the host or installation.
Read more about this topic: Ingres (database)