- Usage example of the data replication
- Vocabulary specific to the replication
- Type of replication
- Files created during a replication
Replication: The different types
Not available with these kinds of connection
The data replication is a powerful feature. The replication is the operation allowing the maintenance of remote databases with identical structures. Each one of these databases evolves independently: different operations are performed on these databases.
Via the replication, the operations performed on each one of the databases are applied to all the other databases.
WINDEV, WINDEV Mobile and WEBDEV allow you to easily perform these operations:
Usage example of the data replication
In a company, the "Customer" file must be accessible to all the salesmen, from their laptop computers as well as from the headquarters. Each salesman updates the file found on his laptop computer and gets regular updates from the main database of the company.
In an application that does not use the replication of data, the database is accessible by network in most cases. The salesman works via a modem connection to the network, with all the constraints regarding access time... Furthermore, all the users must be connected to the same network to access data.
With the replication, each one of the remote computers has its own database. This database (or replica) is identical to the "master" database during its initialization. Regularly, a "Synchronization" of these databases is used to take into account the modifications performed on each one of the different databases.
Remark: The replication is not available when accessing a database via Remote access
Vocabulary specific to the replication
The replication distinguishes between two types of databases:
- The master database
It is the reference database. All the updates are performed on this database:
- modifications performed by the application run on this computer.
- modifications performed on the remote computers and transmitted by the replication.
- The replica database or subscriber database
This remote database is identical to the "Master" database. The modifications performed by the remote computer are applied to this database. The replication transmits these modifications to the "master" database.
Type of replication
Two types of replication can be implemented:
- Unidirectional replication
This type of replication consists in performing an update from the "Master" database to the "Subscriber" databases or from a "Subscriber" database to the "Master" database.
- Bidirectional replication
This type of replication consists in performing an update from the "Master" database to the "Subscriber" databases and from the "Subscriber" databases to the "Master" database.
Files created during a replication
Several types of files specific to the replication are managed when the replication is implemented in a WINDEV application:
- The master replica (RPM extension file): this file is associated with the master database. This file contains the names and identifiers of the different subscriber databases, as well as the date of the last synchronization.
- The subscriber replica (RPL extension file): this file is associated with the subscriber database. This file contains the identifier of the subscriber database, the date of the last synchronization, ...
- The movable replica (or movable media, .RPA file): this file is required to synchronize two remote databases that are not connected. The movable replica contains the information required to update the remote database. This file can be transmitted to the remote database via FTP, email or physical media.
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