Distribution in Non-Mirror Mode

The diagram below represents a DAH run in non-mirror mode. The DAH distributes actions to several different IDOL Servers.

DAH system architecture (non-mirror mode)

The DAH uses either combinator or distributor virtual databases (VDBs) to distribute the actions to one or more specific IDOL Server databases. The VDBs can map to one or more IDOL Server databases, or to other virtual databases that you set up for the DAH. The way a VDB forwards actions depends on its type.

Combinator VDBs

A combinator virtual database forwards actions to all the databases that it represents. The VDB collates and sorts the results before it returns them.

Distributor VDBs

Distributor virtual databases map to a set of identical databases that contain identical data. You determine how the VDB distributes actions by using the DistributionMethod configuration parameter in the DAH configuration file. You can use one of the following methods:

The DAH periodically checks IDOL Servers that are down. If it finds that an IDOL Server has come online again (for example, because the hardware has been rebooted or the network connection repaired), it adds it back into the list of active IDOL servers.