Knowledge Discovery 25.2
Knowledge Discovery Expert

# DIH Distribution Mode Features

This section describes the features that are or are not available for different DIH distribution modes, and describes the data volumes that you can expect in each distribution mode. You can use the two tables on this page to help decide which distribution mode you want to use.

## Features Available in DIH Distribution Modes

The following table describes the features that are available in various DIH distribution modes.

Feature | Simple Distribute | Simple Distribute with DistributeSendMinimal | Batch Mode | DistributeByReference (hash) | DistributeByFields (hash) | Consistent HashingNote UseConsistentHashing is available in hash-based modes (DistributeByReference and DistributeByFields) only. | Round Robin
--- | --- | --- | --- | --- | --- | --- | ---
`KillDuplicates` |  |  |  |  |  |  | Note Deduplication can occur only if you turn on RespectDocumentDate and the duplicates have the same datestamp as the original document.
`KillDuplicates` on any field |  |  |  |  |  |  | Note Deduplication can occur only if you turn on RespectDocumentDate and the duplicates have the same datestamp as the original document.
`KillDuplicates` with `KeepExisting` |  |  |  |  |  |  | Note Deduplication can occur only if you turn on RespectDocumentDate and the duplicates have the same datestamp as the original document.
Can use `PreserveDREADD` or `ConvertToDREADD` |  |  |  |  |  |  |
Quick document parsing (IDX only) | N/A |  | N/A |  |  |  | Note This option is available only if you turn on RespectDocumentDate. Otherwise, documents pass through to the current server without the need for parsing.
Can distribute `DREREPLACE` data |  |  |  |  |  | Note For DistributeByReference mode used with UseConsistentHashing only. | Note This option is possibly only if the DREREPLACE data contains a datestamp for target documents in the #DREDATE field.
Change the number of childrenNote This indicates that you can change the number of child servers without affecting deduplication, and without needing to reindex content. |  |  |  |  |  | Note DIH minimizes the number of documents that need reindexing, and performs this operation automatically. |
Automatic redistribution when adding engines |  |  |  |  |  |  |
Automatic redistribution when removing engines |  |  |  |  |  |  |
Redistribute when children are down | Note Enabling redistribute might mean that deduplication does not occur properly for documents in the offline child server. |  |  |  |  |  |
Weighted children |  |  |  |  |  |  |
Update-only children |  |  |  |  |  |  |
Respect child fullness |  |  |  |  |  |  |
Take children up or down for query |  |  |  |  |  |  |
Clear data in oldest child |  |  |  |  |  |  |

## Data Transfer Volumes for DIH Distribution Modes

The following table describes the data transfer volumes for the different DIH distribution modes in terms of the fraction of the number of documents in the incoming IDX or XML. These approximately correspond to data file size (ignoring marginal overheads such as XML headers). However, if your documents differ widely in size or you index in small batches, these values will only emerge as long-term averages.

In the table:

- N is the number of server groups

- M is the total number of child servers

- r is the number of replicas configured in Consistent Hash mode

Amount of Data | Simple Distribute | Simple Distribute with ConvertToDREADD | Simple Distribute with DistributeSendMinimal | Batch Mode | Hash-Based Modes | Hash-Based Modes with Consistent Hashing | Round Robin | Round Robin with RespectDocumentDate
--- | --- | --- | --- | --- | --- | --- | --- | ---
Saved to incoming | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1
Read by the DIH (parsing) | - | - | 1 | - | 1 | 1 | - | 1
Written by the DIH (parsing) | - | - | 1Note In DistributeSendMinimal mode, DIH sends each child server the full content of teh documents that it must index, plus a minimal representation of documents that it must deduplicate, containing only the necessary reference fields for deduplication. For reasonable large documents, these minimal documents make a negligible contribution to the volume of data sent to the child, which will be a little more than 1/N. For very small documents, the size of the minimal representation might become an appreciable fraction of the original, and the observed savings in transmitted data might be correspondingly lower. | - | M/N | (r+1)M/NNote When consistent hashing is turned on, the DIH inserts a tracking field into each document to allow it to redistribute data. For all but the very smallest of documents, the contribution of the additional field to the overall volume of data is negligible. | - | M/N
Total read or sent for indexing to child servers | M | - | M/NNote In DistributeSendMinimal mode, DIH sends each child server the full content of teh documents that it must index, plus a minimal representation of documents that it must deduplicate, containing only the necessary reference fields for deduplication. For reasonable large documents, these minimal documents make a negligible contribution to the volume of data sent to the child, which will be a little more than 1/N. For very small documents, the size of the minimal representation might become an appreciable fraction of the original, and the observed savings in transmitted data might be correspondingly lower. | M/N | M/N | (r+1)M/NNote When consistent hashing is turned on, the DIH inserts a tracking field into each document to allow it to redistribute data. For all but the very smallest of documents, the contribution of the additional field to the overall volume of data is negligible. | M/N | M/N
Volume received per child for one job | 1 | - | 1/NNote In DistributeSendMinimal mode, DIH sends each child server the full content of teh documents that it must index, plus a minimal representation of documents that it must deduplicate, containing only the necessary reference fields for deduplication. For reasonable large documents, these minimal documents make a negligible contribution to the volume of data sent to the child, which will be a little more than 1/N. For very small documents, the size of the minimal representation might become an appreciable fraction of the original, and the observed savings in transmitted data might be correspondingly lower. | 0 or 1Note In Batch Mode, each child server received all or none of the incoming data, with the target server rotating between index actions. | 1/N | (r+1)NNote When consistent hashing is turned on, the DIH inserts a tracking field into each document to allow it to redistribute data. For all but the very smallest of documents, the contribution of the additional field to the overall volume of data is negligible. | 0 or 1 | 0 or 1Note This value assumes that most documents are new additions and do not carry a historic data field value.
Long term average value per child | 1 | - | 1/NNote In DistributeSendMinimal mode, DIH sends each child server the full content of teh documents that it must index, plus a minimal representation of documents that it must deduplicate, containing only the necessary reference fields for deduplication. For reasonable large documents, these minimal documents make a negligible contribution to the volume of data sent to the child, which will be a little more than 1/N. For very small documents, the size of the minimal representation might become an appreciable fraction of the original, and the observed savings in transmitted data might be correspondingly lower. | 1/N | 1/N | (r+1)NNote When consistent hashing is turned on, the DIH inserts a tracking field into each document to allow it to redistribute data. For all but the very smallest of documents, the contribution of the additional field to the overall volume of data is negligible. | 1/N | 1/N

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Version 25.2 | Last updated April 2025

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Product: Knowledge Discovery 25.2

Topic Title: DIH Distribution Mode Features