Configuring Data

Caché stores data — persistent multidimensional arrays (globals) as well as executable code (routines) — in one or more physical structures called databases. A database consists of one or more physical files stored in the local operating system. A Caché system may (and usually does) have multiple databases.

Each Caché system maintains a database cache — a local, shared memory buffer used to cache data retrieved from the physical databases. This cache greatly reduces the amount of costly I/O operations required to access data and provides much of the performance benefits of Caché. (For information about allocating the database cache, see Memory and Startup Settings.)

Caché applications access data by means of a namespace. A namespace provides a logical view of data (globals and routines) stored in one or more physical databases. A Caché system may (and usually does) have multiple namespaces. Caché maps the data visible in a logical namespace to one or more physical databases. This mapping provides applications with a powerful mechanism for changing an application’s physical deployment without changing application logic.

In the simplest case, there is a one-to-one correspondence between a namespace and a database, but many systems take advantage of the ability to define a namespace that provides access to data in multiple databases. For example, a system could have multiple namespaces, each of which provides a different logical view of the data stored within one or more physical databases.

For more details, see the following sections:

See the Config entries in the InterSystems Class Reference for information about updating namespaces, databases, and mappings programmatically.