Caché Distributed Data Management Guide
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One of the most powerful and unique features of Caché is the ability to efficiently distribute data and application logic among a number of server systems.

The underlying technology behind this feature is the Enterprise Cache Protocol (ECP): a distributed data caching architecture that manages the distribution of data and locks among a heterogeneous network of server systems.
Unlike other “multi-tier” architectures, ECP is primarily a configuration option. That is, you do not have to use special code or development techniques to create distributed database applications. This provides several important advantages over other technologies:
This overview covers the following topics:
ECP Features
ECP provides the following features:
Besides providing a high degree of system availability, the automatic behavior of ECP makes a system easier to manage. For example, it is possible to take an ECP data server offline temporarily for a software upgrade and restore it without having to perform any operations on the ECP application server systems.
Uses for ECP
The primary reasons to use ECP are:
For information on configuring a system for ECP, see the Configuring Distributed Systems chapter.
ECP Architecture
The architecture and operation of ECP is conceptually simple. ECP provides a way to efficiently share data, locks, and executable code among multiple Caché systems. Data and code are stored remotely, but are cached locally to provide efficient access with minimal network traffic.
For more information on application development and design using ECP, see the Developing Distributed Applications chapter.
Databases and Namespaces
To better understand how ECP works, it is first helpful to review how databases, namespaces, and caching work in Caché.
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 many of the performance benefits of Caché.
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 (which disk drives are used, etc.) without changing application logic. This same mechanism, in conjunction with ECP, is what makes it possible to redeploy applications among multiple, networked systems with few or no application changes.
ECP Application Servers and Data Servers
An ECP configuration consists of a number of Caché systems that are visible to one another across a TCP/IP-based network. There are two roles a Caché system can play in an ECP configuration:
A Caché system can simultaneously act as both an ECP data server and an ECP application server. However, one Caché instance cannot act as an ECP data server for the data it receives as an application server of another ECP data server.
In an ECP configuration, each ECP data server is responsible for the following:
In an ECP configuration, each ECP application server is responsible for the following:
ECP Connections and Recovery
ECP automatically establishes and maintains network connections between application server and data server systems. If a connection is broken, ECP automatically reestablishes the connection and restores the operating state of the system, if possible.
For more information on ECP connections, see the Monitoring Distributed Applications chapter.
For more information on ECP recovery, see the Developing Distributed Applications chapter.

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