Editing Ingres (database) (section)

==Installation==
Ingres can be installed as a client (Client Installation) or as a server (Server Installation), the client does not have a database associated with it, but it allows you to access the database created in the server installation.

A typical site installs the Ingres client for workers on the computers that will interact with the Ingres server at the core of the site.

Note that the expression "instance" is synonymous with "installation".

An installation can be thought of as a collection of server processes, shared memory, and semaphores for inter-process communication, as well as disk files used for transaction processing and recovery in the event of a host or installation failure.

=== Install ID ===
An installation is often named by its installation ID. This identifier consists of two case-sensitive characters, starting with a letter. The default is II. The installation ID is used to calculate which ports the Ingres servers will listen on. For example, "II" indicates that the servers are listening on port 21064 and 7 ports after it.

Any host (machine or virtual machine) can have multiple installations of Ingres, but each installation must have a unique identifier to ensure that clients and components interact with the correct installation.

One installation can use multiple installation IDs. A classic example is when you need to run more than 8 processes on the server. Also, while Ingres database servers (iidbms) and Ingres communication servers (iigcc) conventionally use the same installation ID, there is no requirement to do so.

=== Installation paths ===
Some important paths must be assigned at the location where the installation was created. The paths will not change without reinstallation, so you should take care to choose them.

The paths are shown in the following table. Note that the "II_" prefix does not indicate that these paths are for the "II" installation. Each installation, regardless of its ID, will have its own set of these variables.

{| class="wikitable" border="1"
|-
! Name
! Purpose
|- 
|II_SYSTEM
|Setup binary files, utilities, text files used for configuration, etc.
|-
|II_DATABASE
|Location of installation master data.
|-
|II_CHECKPOINT
|Database backup location.
|-
|II_JOURNAL
|Location where database installation transactions are logged. The logs use the recovery system to provide point-of-failure recovery. Can be used for audit purposes.
|-
|II_DUMP
|Location where "dump" installation files are stored. They can be generated during "online" database backups and [ what? ] to restore.
|-
|II_WORK
|Used to store work files generated by the server when querying the database.
|}

=== Databases ===
An Ingres installation (or instance) can support multiple databases, each owned by any user known to the installation. The installation allows multiple databases to be accessed at the same time. The number of databases is a configurable value. Note that this simply limits the number of databases available at any one time and many more databases can be created.

When creating an Ingres server installation, the databases "iidbdb" and "imadb" will be created, owned by the user "$ingres". The iidbdb database, also known as the "Master Catalog database", contains many special tables to manage the installation itself. The imadb (Management Architecture database) database also includes registered objects used to manage the installation.

Of particular note is that databases are not pre-sized. Each database in the installation is allowed to grow in size as much as the free disk space allows.