Database Basics

Database Configuration

For any database, InterSystems IRIS requires the following configuration details:

• Logical name for the database.

• Directory in which the IRIS.DAT file resides. When you create a database in the Management Portal, you are prompted to choose or create a subdirectory within the system manager’s directory (install-dir/Mgr), but you can store the database file in any convenient directory.

  Tip:

  It is convenient to use the same string for the logical name and for the directory that contains the IRIS.DAT file. The system-provided InterSystems IRIS databases follow this convention.

Additional options include the following:

• Default directory to use for file streams used by this database.

  This is important because your users will need write access to this directory; if not, your code will not be able to create file streams.

• Collation of new globals.

• Initial size and other physical characteristics.

• Option to enable or disable journaling. Journaling tracks changes made to an InterSystems IRIS database, for up-to-the-minute recovery after a crash or restoring your data during system recovery.

  In most cases, it is best to enable journaling. However, you might want to disable journaling for designated temporary work spaces; for example, the IRISTEMP database is not journaled.

• Option to mount this database for read-only use.

  If a user tries to set a global in a read-only database, InterSystems IRIS returns a <PROTECT> error.

In most cases, you can create, delete, or modify database attributes while the system is running.

Database Features

With each database, InterSystems IRIS provides physical integrity guarantees for both the actual data and the metadata that organizes it. This integrity is guaranteed even if an error occurs during writes to the database.

The databases are automatically extended as needed, without manual intervention. If you expect a particular database to grow and you can determine how large it will become, you can “pre-expand” it by setting its initial size to be near the expected eventual size. If you do so, the performance is better.

InterSystems IRIS provides a number of strategies that allow high availability and recoverability. These include:

• Journaling — Introduced earlier.

• Mirroring — Provides rapid, reliable, robust, automatic failover between two InterSystems IRIS systems, making mirroring the ideal automatic failover high-availability solution for the enterprise.

• Clustering — There is full support of clustering on operating systems that provide it.

InterSystems IRIS has a technology for distributing data and application logic and processing among multiple systems. It is called the Enterprise Cache Protocol (ECP). On a multiserver system, a network of InterSystems IRIS database servers can be configured as a common resource, sharing data storage and application processing, with the data distributed seamlessly among them. This provides increased scalability as well as automatic failover and recovery.

Database Portability

InterSystems IRIS databases are portable across platforms and across versions, with the following caveat:

• On different platforms, any file is either big-endian (that is, most-significant byte first) or little-endian (least-significant byte first).

  InterSystems IRIS provides a utility to convert the byte order of an InterSystems IRIS database; it is called cvendian. This is useful when moving a database among platforms of the two types.