Welcome to Pervasive DataExchange

A Basic Introduction to Pervasive DataExchange

Thank you for purchasing Pervasive DataExchange. This chapter contains the following topics:

What’s New in Pervasive DataExchange

About Pervasive DataExchange

Overview of How Pervasive DataExchange Works

Where to Install DataExchange

DataExchange Licensing

What’s New in Pervasive DataExchange

The following features are new in this release of Pervasive DataExchange:

Support for the current version of Pervasive PSQL.

Use and administration of replication features through the Java user interface in Pervasive PSQL.

Support for replication of table names beginning with the prefix “PDC”

 

About Pervasive DataExchange

Pervasive DataExchange is Pervasive Software’s database replication solution. It reliably moves data between two or more Pervasive PSQL databases to maintain a current backup system, drive data into reporting servers, or synchronize multiple remote databases. In short, Pervasive DataExchange offers several ways to help you replicate your data.

Pervasive DataExchange is available in two editions: Real-Time Backup and Data Synchronization.The following table summarizes the features of Pervasive DataExchange based on the edition.

Table 1-1

Comparison of Pervasive DataExchange Editions

Feature	Edition
	Real-Time Backup	Data Synchronization
One-way replication	4	4
Two-way replication		4
Scripted set up	4
Data-driven replication		4

Overview of How Pervasive DataExchange Works

The DataExchange technology works by capturing and sharing changes from one Pervasive PSQL database to other databases in a DataExchange replication network. Each database is augmented with DataExchange, which adds two software components to a Pervasive PSQL database: the Replication Event Handler and the Replication Engine.

The Replication Event Handler (REH) plugs directly into the Pervasive PSQL database engine. Specifically, the REH is a set of DLLs that operate within the database engine, so if the database is running, the replication event handler is running as well. The database engine activates the REH when there is a change event (insert, update, delete). The REH then makes note of the event in one of its private control tables.

The Replication Engine is a separate process that performs the actual replication task. It reads the control tables to determine what records have changed since the last replication session. It then groups these changes into packets and shares them with the other replication engines participating in a DataExchange network. These other engines then apply the updates to their own databases. The replication process occurs either continuously, at scheduled intervals, or on demand. The replication engine does not require constant network connectivity, so DataExchange is suitable for scenarios with intermittent connectivity, like remote users with dialup connections.

Notification Agent

The notification agent, or agent for short, is another component installed by DataExchange. Its purpose is to initiate an e-mail if a replication failure occurs. The agent requires the basic Simple Mail Transfer Protocol (SMTP) to communicate with a mail server.

Note that the agent is installed only if the machine contains the Pervasive PSQL Server product. The agent is not available if you install DataExchange on a machine with the Pervasive PSQL Workgroup product.

See dxagent in Pervasive DataExchange User’s Guide.

Replication-specific Files

DataExchange adds its own tables on the machine where replication executes. It uses two types of tables: system configuration and replication control. Configuration tables record information such as the databases being replicated, the sites to which data is replicated, and replication schedules.

Control tables shadow data files and track the replication state of each record in the data. Each data table or file has a control table counterpart. Similarly, each data record has a companion control table record. Through the control tables, the replication engine determines what records need to be replicated when.

DataExchange tables for replication configuration and control can reside with the files to be replicated or separately in their own database. The choice of location depends on your replication needs. Replication of entire tables can be done with a separate replication database.

Every kind of available replication solution is covered in Pervasive DataExchange User’s Guide.

Where to Install DataExchange

Pervasive DataExchange must be installed on the same computer as the Pervasive PSQL Server or Workgroup engine. See also Preparing to Install Pervasive DataExchange.

DataExchange Licensing

Pervasive DataExchange Data Synchronization Edition requires an activation license for each machine involved in a replication network. A replication network consists of a First Site and one or more Partner Sites. The installation program prompts you to enter a license string and decodes it to ensure that it is valid.

You may install an evaluation version of Pervasive DataExchange without a license. At the end of the evaluation period, the replication engine returns an error when it attempts to start. Use the Event Viewer of your operating system to view the error in the Application event log.

You may initially install an evaluation version then later apply an activation license. Use the following steps to replace an evaluation license with a nonevaluation license.

To upgrade an evaluation license

1	Obtain the license key from one of the following locations:

Case of the DataExchange installation CD

Product registration card

Printed license agreement

2	If you need to purchase a license, contact Sales Support at Pervasive Software (salessupport@pervasive.com). See also How to Get Additional Help in Pervasive DataExchange User’s Guide.

3	Apply the license using the Pervasive PSQL License Administrator utility. See the License Administrator chapter in Pervasive PSQL User's Guide.