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 | Data Replication Technology |  |
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Pervasive DataExchange™ leverages sophisticated database replication technology to ensure your mission-critical
data is always where you need it when you need it.
The DataExchange technology works by capturing and sharing changes from one Pervasive.SQL™ database to other
databases in a DataExchange replication network. Each database is augmented with DataExchange, which adds
two software components to a Pervasive.SQL database, the Replication Event Handler and the Replication Engine.
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The Replication Event Handler (REH) plugs directly into the Pervasive.SQL 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 too. 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.
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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.
The DataExchange engine has the following advanced capabilities:
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Replication normally occurs at the transactional level, so data definition files (DDFs) are not required.
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Update packets are encrypted using a 128-bit key. This enhances security by eliminating the possibility
of unauthorised viewing of the database changes.
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Conflicts are detected and resolved. Conflicts occur when the same record in two different databases is
edited at the same time. In most applications, data conflicts are rare or nonexistent. In cases
where data conflicts may occur, there are default and user definable resolution rules.
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Network topology is flexible. While most DataExchange networks include only two databases replicating back
and forth, multiple database scenarios and organisations are possible. Supported topologies include ring,
hub and spoke, peer-to-peer, and hierarchical.
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Fine-grained data segmentation is possible. This includes vertical (particular columns are treated as a
unit), horizontal (groups of records are treated as a unit) and referential (records from different tables that
are linked by a referential integrity structure are treated as a unit). This allows tight control over
what set of database content is replicated where.
In addition, DataExchange includes a full suite of design, maintenance and monitoring tools.
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