# UseConsistentHashing

Set this parameter to `true` to use the DIH consistent hashing mode with the DistributeByReference or simple DistributeByFields (without DistributeByFieldsValues) distribution modes. In consistent hashing mode, you can add, remove, or change the weight of child servers in your Distributed Index Handler without having to reindex all your content.

In this mode, Distributed Index Handler distributes documents among a large, fixed number of virtual nodes, and then assigns these nodes to one or more child servers. When you change the number or weight of child servers, you can use the DREREDISTRIBUTE index action to redistribute the virtual nodes between the new set of servers without reindexing all the data.

NOTE: You cannot use consistent hashing mode in a distribution architecture with tiered DIHs.

To use consistent hashing, you must configure a new field process in all of the child servers to set the `*/DREVNODE` to use the `ReferenceType`, and `TrimSpaces`. You might also want to use the `HiddenType` property for this field. You must use a new field process, rather than adding it to an existing reference field process. For example:

    [FieldProcessing]
    0=SetVNodeReferenceField

    [SetVNodeReferenceField]
    Property=VNodeReferenceField
    PropertyFieldCSVs=*/DREVNODE

    [VNodeReferenceField]
    ReferenceType=TRUE
    TrimSpaces=TRUE
    HiddenType=TRUE

For more details about field processes, refer to the IDOL Server Reference.

NOTE: When you initially switch from the default mode to consistent hashing mode, you must reindex your data.

For more information about consistent hashing mode, refer to the Distributed Index Handler Administration Guide.

Type: | Boolean
Default: | False
Required: | No
Configuration Section: | Server
Example: | `UseConsistentHashing=true`
See Also: | DistributeByReference DistributeByFields Replicas VirtualNodes DREREDISTRIBUTE index action

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