Using Caché Multi-Dimensional Storage - InterSystems ...

Introduction
1.3 Use in Applications
Within Caché applications, globals are used in many ways, including:
• As the underlying storage mechanism shared by the object and SQL engines.
• As the mechanism used to provide a variety of indices, including bitmap indices, for
object and SQL data.
• As a workspace for performing certain operations that may not fit within process memory.
For example, the SQL engine uses temporary globals for sorting data when there is no
preexisting index available for this purpose.
• For performing specialized operations on persistent objects or SQL tables that are difficult
or inefficient to express in terms of object or SQL access. For example, you can define
a method (or stored procedure or Web method) to perform specialized analysis on data
held in a table. By using methods, such an operation is completely encapsulated; the
caller simply invokes the method.
• To implement application-specific, customized storage structures. Many applications
have the need to store data that is difficult to express relationally. Using globals you can
define custom structures and make them available to outside clients via object methods.
• For a variety of special purpose data structures used by the Caché system, such as configuration
data, class definitions, error messages, and executable code.
Globals are not constrained by the confines of the relational model. They provide the freedom
to develop customized structures optimized for specific applications. For many applications,
judicious use of globals can be a secret weapon delivering performance that relational application
developers can only dream about.
Whether your application makes direct use of globals or not, it is useful to understand their
operation. Understanding globals and their capabilities will help you to design more efficient
applications as well as provide help with determining the optimal deployment configuration
for your applications.
4 Using Caché Multi-Dimensional Storage