Example: Virtual Databases

A DAH has three child servers:

  • server 0 has a database of dog information, called dogs.

  • server 1 has:

    • a database of cat information, called cats.
    • a database of parrot information, called parrots.
  • server 2 has a database of flower information, called flowers.

Configuration

The following DAH VDB configuration queries all information about pets:

[VDB0]
Name=pets
MapsTo=0:dogs,1:cats,1:parrots
Type=combinator

In this example, note that:

  • You do not have to reference all child servers in the MapsTo parameter.

  • You can reference the same child server multiple times.

Query

When DAH receives a query with DatabaseMatch set to pets, DAH sends:

  • the query with DatabaseMatch set to dogs to server 0.

  • the query with DatabaseMatch set to cats+parrots to server 1.

    TIP: There are other advanced distribution options for VDBs, such as multi-stage querying. For more information, refer to the DAH Reference.